0000822818-21-000053 | 10-Q | XBRL Viewer

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Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2021	Oct. 29, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-34223
Entity Registrant Name	CLEAN HARBORS, INC
Entity Incorporation, State or Country Code	MA
Entity Tax Identification Number	04-2997780
Entity Address, Address Line One	42 Longwater Drive
Entity Address, City or Town	Norwell
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02061-9149
City Area Code	781
Local Phone Number	792-5000
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	CLH
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		54,412,116
Entity Central Index Key	0000822818
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 646,663	$ 519,101
Short-term marketable securities	64,844	51,857
Accounts receivable, net of allowances aggregating $41,807 and $44,749, respectively	703,199	611,534
Unbilled accounts receivable	69,912	55,681
Inventories and supplies	228,682	220,498
Prepaid expenses and other current assets	70,864	67,051
Total current assets	1,784,164	1,525,722
Property, plant and equipment, net	1,508,356	1,525,298
Other assets:
Operating lease right-of-use assets	137,429	150,341
Goodwill	543,028	527,023
Permits and other intangibles, net	366,497	386,620
Other	14,825	16,516
Total other assets	1,061,779	1,080,500
Total assets	4,354,299	4,131,520
Current liabilities:
Current portion of long-term debt	7,535	7,535
Accounts payable	286,565	195,878
Deferred revenue	86,589	74,066
Accrued expenses and other current liabilities	299,427	295,823
Current portion of closure, post-closure and remedial liabilities	23,288	26,093
Current portion of operating lease liabilities	36,497	36,750
Total current liabilities	739,901	636,145
Other liabilities:
Closure and post-closure liabilities, less current portion of $10,219 and $13,903, respectively	82,809	74,023
Remedial liabilities, less current portion of $13,069 and $12,190, respectively	97,747	102,623
Long-term debt, less current portion	1,546,284	1,549,641
Operating lease liabilities, less current portion	102,093	114,258
Deferred tax liabilities	231,663	230,097
Other long-term liabilities	90,242	83,182
Total other liabilities	2,150,838	2,153,824
Commitments and contingent liabilities (See Note 16)
Stockholders’ equity:
Authorized 80,000,000 shares; issued and outstanding 54,409,894 and 54,772,696 shares, respectively	544	548
Additional paid-in capital	539,747	582,749
Accumulated other comprehensive loss	(200,716)	(211,477)
Accumulated earnings	1,123,985	969,731
Total stockholders’ equity	1,463,560	1,341,551
Total liabilities and stockholders’ equity	$ 4,354,299	$ 4,131,520

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 41,807	$ 44,749
Closure and post-closure liabilities, current portion	10,219	13,903
Remedial liabilities, current portion	$ 13,069	$ 12,190
Common stock, per value (in USD per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	80,000,000	80,000,000
Common stock, issued shares (in shares)	54,409,894	54,772,696
Common stock, outstanding shares (in shares)	54,409,894	54,772,696

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 951,479	$ 779,344	$ 2,686,085	$ 2,347,907
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	639,232	511,629	1,817,654	1,588,976
Selling, general and administrative expenses	133,164	106,544	378,911	339,690
Accretion of environmental liabilities	2,799	2,822	8,625	8,149
Depreciation and amortization	71,451	74,470	215,206	221,497
Income from operations	104,833	83,879	265,689	189,595
Other income (expense), net	199	2,268	(2,509)	(597)
Loss on sale of businesses	0	(118)	0	(3,376)
Interest expense, net of interest income of $653, $1,236, $1,712 and $2,902, respectively	(17,984)	(17,407)	(53,953)	(54,848)
Income before provision for income taxes	87,048	68,622	209,227	130,774
Provision for income taxes	21,605	13,712	54,973	35,269
Net income	$ 65,443	$ 54,910	$ 154,254	$ 95,505
Earnings Per Share [Abstract]
Basic (in dollars per share)	$ 1.20	$ 0.99	$ 2.83	$ 1.72
Diluted (in dollars per share)	$ 1.20	$ 0.99	$ 2.81	$ 1.71
Shares used to compute earnings per share - Basic (in shares)	54,411	55,592	54,553	55,646
Shares used to compute earnings per share - Diluted (in shares)	54,707	55,738	54,862	55,832
Service revenues
Revenues:
Total revenues	$ 744,549	$ 681,306	$ 2,141,820	$ 2,039,012
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	508,498	428,735	1,451,498	1,332,516
Product revenues
Revenues:
Total revenues	206,930	98,038	544,265	308,895
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 130,734	$ 82,894	$ 366,156	$ 256,460

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Interest income	$ 653	$ 1,236	$ 1,712	$ 2,902

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 65,443	$ 54,910	$ 154,254	$ 95,505
Other comprehensive (loss) income, net of tax:
Unrealized (losses) gains on available-for-sale securities	(18)	(121)	(140)	111
Unrealized (losses) gains on interest rate hedge	(99)	(123)	2,660	(21,505)
Reclassification adjustment for losses on interest rate hedge included in net income	2,532	2,468	7,474	5,696
Foreign currency translation adjustments	(14,242)	10,161	767	(13,695)
Other comprehensive (loss) income, net of tax	(11,827)	12,385	10,761	(29,393)
Comprehensive income	$ 53,616	$ 67,295	$ 165,015	$ 66,112

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 154,254	$ 95,505
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	215,206	221,497
Allowance for doubtful accounts	7,186	10,441
Amortization of deferred financing costs and debt discount	2,718	2,688
Accretion of environmental liabilities	8,625	8,149
Changes in environmental liability estimates	341	9,050
Deferred income taxes	5,202	0
Other expense, net	2,509	597
Stock-based compensation	12,786	12,739
Loss on sale of businesses	0	3,376
Environmental expenditures	(12,223)	(8,816)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(113,601)	23,969
Inventories and supplies	(12,882)	(9,554)
Other current and non-current assets	(10,785)	(19,320)
Accounts payable	86,974	(63,898)
Other current and long-term liabilities	21,916	31,009
Net cash from operating activities	368,226	317,432
Cash flows used in investing activities:
Additions to property, plant and equipment	(146,654)	(150,357)
Proceeds from sale and disposal of fixed assets	16,424	7,307
Acquisitions, net of cash acquired	(22,819)	(8,839)
Proceeds from sale of businesses, net of transactional costs	0	7,712
Additions to intangible assets including costs to obtain or renew permits	(2,659)	(1,863)
Proceeds from sale of available-for-sale securities	83,226	39,141
Purchases of available-for-sale securities	(96,785)	(53,397)
Net cash used in investing activities	(169,267)	(160,296)
Cash flows used in financing activities:
Change in uncashed checks	(4,323)	381
Tax payments related to withholdings on vested restricted stock	(7,383)	(4,407)
Repurchases of common stock	(48,409)	(39,542)
Deferred financing costs paid	(150)	0
Payments on finance leases	(5,845)	(2,755)
Principal payments on debt	(5,652)	(5,652)
Borrowing from revolving credit facility	0	150,000
Payment on revolving credit facility	0	(150,000)
Net cash used in financing activities	(71,762)	(51,975)
Effect of exchange rate change on cash	365	(1,446)
Increase in cash and cash equivalents	127,562	103,715
Cash and cash equivalents, beginning of period	519,101	371,991
Cash and cash equivalents, end of period	646,663	475,706
Cash payments for interest and income taxes:
Interest paid	61,807	66,000
Income taxes paid, net of refunds	48,202	14,195
Non-cash investing activities:
Property, plant and equipment accrued	11,561	11,732
ROU assets obtained in exchange for operating lease liabilities	18,528	19,993
ROU assets obtained in exchange for finance lease liabilities	$ 18,704	$ 28,333

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings
Balance beginning of period (in shares) at Dec. 31, 2019		55,798
Balance beginning of period at Dec. 31, 2019	$ 1,269,813	$ 558	$ 644,412	$ (210,051)	$ 834,894
Increase (Decrease) in Stockholders' Equity
Net income	11,572				11,572
Other comprehensive (loss) income	(59,306)			(59,306)
Stock-based compensation	3,291		3,291
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		59
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(2,224)	$ 1	(2,225)
Repurchases of common stock (in shares)		(302)
Repurchases of common stock	(17,341)	$ (3)	(17,338)
Balance ending of period (in shares) at Mar. 31, 2020		55,555
Balance ending of period at Mar. 31, 2020	1,205,805	$ 556	628,140	(269,357)	846,466
Balance beginning of period (in shares) at Dec. 31, 2019		55,798
Balance beginning of period at Dec. 31, 2019	1,269,813	$ 558	644,412	(210,051)	834,894
Increase (Decrease) in Stockholders' Equity
Net income	95,505
Other comprehensive (loss) income	(29,393)
Balance ending of period (in shares) at Sep. 30, 2020		55,246
Balance ending of period at Sep. 30, 2020	1,304,715	$ 552	613,208	(239,444)	930,399
Balance beginning of period (in shares) at Mar. 31, 2020		55,555
Balance beginning of period at Mar. 31, 2020	1,205,805	$ 556	628,140	(269,357)	846,466
Increase (Decrease) in Stockholders' Equity
Net income	29,023				29,023
Other comprehensive (loss) income	17,528			17,528
Stock-based compensation	2,786		2,786
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		58
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(1,171)		(1,171)
Balance ending of period (in shares) at Jun. 30, 2020		55,613
Balance ending of period at Jun. 30, 2020	1,253,971	$ 556	629,755	(251,829)	875,489
Increase (Decrease) in Stockholders' Equity
Net income	54,910				54,910
Other comprehensive (loss) income	12,385			12,385
Stock-based compensation	6,662		6,662
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		35
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(1,012)		(1,012)
Repurchases of common stock (in shares)		(402)
Repurchases of common stock	(22,201)	$ (4)	(22,197)
Balance ending of period (in shares) at Sep. 30, 2020		55,246
Balance ending of period at Sep. 30, 2020	1,304,715	$ 552	613,208	(239,444)	930,399
Balance beginning of period (in shares) at Dec. 31, 2020		54,773
Balance beginning of period at Dec. 31, 2020	1,341,551	$ 548	582,749	(211,477)	969,731
Increase (Decrease) in Stockholders' Equity
Net income	21,736				21,736
Other comprehensive (loss) income	11,948			11,948
Stock-based compensation	3,480		3,480
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		78
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(3,719)	$ 1	(3,720)
Repurchases of common stock (in shares)		(300)
Repurchases of common stock	(26,546)	$ (3)	(26,543)
Balance ending of period (in shares) at Mar. 31, 2021		54,551
Balance ending of period at Mar. 31, 2021	1,348,450	$ 546	555,966	(199,529)	991,467
Balance beginning of period (in shares) at Dec. 31, 2020		54,773
Balance beginning of period at Dec. 31, 2020	1,341,551	$ 548	582,749	(211,477)	969,731
Increase (Decrease) in Stockholders' Equity
Net income	154,254
Other comprehensive (loss) income	10,761
Balance ending of period (in shares) at Sep. 30, 2021		54,410
Balance ending of period at Sep. 30, 2021	1,463,560	$ 544	539,747	(200,716)	1,123,985
Balance beginning of period (in shares) at Mar. 31, 2021		54,551
Balance beginning of period at Mar. 31, 2021	1,348,450	$ 546	555,966	(199,529)	991,467
Increase (Decrease) in Stockholders' Equity
Net income	67,075				67,075
Other comprehensive (loss) income	10,640			10,640
Stock-based compensation	3,305		3,305
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		42
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(1,020)		(1,020)
Repurchases of common stock (in shares)		(200)
Repurchases of common stock	(18,863)	$ (2)	(18,861)
Balance ending of period (in shares) at Jun. 30, 2021		54,393
Balance ending of period at Jun. 30, 2021	1,409,587	$ 544	539,390	(188,889)	1,058,542
Increase (Decrease) in Stockholders' Equity
Net income	65,443				65,443
Other comprehensive (loss) income	(11,827)			(11,827)
Stock-based compensation	6,001		6,001
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		50
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(2,644)		(2,644)
Repurchases of common stock (in shares)		(33)
Repurchases of common stock	(3,000)	$ 0	(3,000)
Balance ending of period (in shares) at Sep. 30, 2021		54,410
Balance ending of period at Sep. 30, 2021	$ 1,463,560	$ 544	$ 539,747	$ (200,716)	$ 1,123,985

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (PARENTHETICAL) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Stockholders' Equity [Abstract]
Common stock, $0.01 par value:	$ 0.01	$ 0.01

BASIS OF PRESENTATION	9 Months Ended
BASIS OF PRESENTATION	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATIONThe accompanying consolidated interim financial statements are unaudited and include the accounts of Clean Harbors, Inc. and its subsidiaries (collectively, “Clean Harbors,” the “Company” or "we") and have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) and, in the opinion of management, include all adjustments which are of a normal recurring nature and are necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented. Management has made estimates and assumptions affecting the amounts reported in the Company's consolidated interim financial statements and accompanying footnotes; actual results could differ from those estimates and judgments. The results for interim periods are not necessarily indicative of results for the entire year or any other interim periods. The financial statements presented herein should be read in conjunction with the financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020.

SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
SIGNIFICANT ACCOUNTING POLICIES	Sep. 30, 2021
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES The Company's significant accounting policies are described in Note 2, "Significant Accounting Policies," in the Company's Annual Report on Form 10-K for the year ended December 31, 2020. There have been no material changes in these policies or their application except for the changes described below. Changes in Operating Segments During the first quarter of 2021, the Company reorganized its Safety-Kleen business. The collection services for waste oil, used oil filters, antifreeze and related items and bulk blended oil sales operations were combined with the Safety-Kleen Oil business to form the Safety-Kleen Sustainability Solutions business. Under this structure, Safety-Kleen Sustainability Solutions will encompass both sides of the spread the Company manages in its re-refinery business, and the Company expects this change to drive additional growth in its sustainable lubricant products and related services. Concurrently with this change, the Company consolidated the Safety-Kleen Environmental branches' core offerings, including containerized waste, parts washer and vacuum services, into the legacy Clean Harbors Environmental Services sales and service operations. The Company expects this change to foster enhanced cross-selling opportunities within the environmental businesses and increase market presence with small quantity generators of hazardous waste. In restructuring the operations of the Company in this manner, the information that the chief operating decision maker regularly reviews for purposes of allocating resources and assessing performance changed to conform to this new operating structure of the business and the Company reevaluated the identification of its operating segments. In accordance with ASC 280, Segment Reporting, Environmental Services and Safety-Kleen Sustainability Solutions are the Company's operating segments and reportable segments starting in the first quarter of 2021, with the operations not managed through the Company's operating segments described above continuing to be recorded as Corporate Items. See Note 17, "Segment Reporting" for more information. The amounts presented for the three and nine months ended September 30, 2020 and any segment information presented as of December 31, 2020 have been recast to reflect the impact of such changes. In addition, certain intercompany transactions previously recorded in Corporate Items have been allocated to the segments. These reclassifications and adjustments had no effect on the consolidated statements of operations, consolidated statements of comprehensive income (loss), consolidated statements of cash flows or consolidated statements of stockholders' equity for any of the periods presented.

REVENUES

9 Months Ended

Sep. 30, 2021

Revenue from Contract with Customer [Abstract]

REVENUES

The Company generates revenues through its Environmental Services and Safety-Kleen Sustainability Solutions operating segments. The Company's Environmental Services operating segment has four sources of revenue and the Safety-Kleen Sustainability Solutions operating segment has two sources of revenue.

Technical Services—Technical Services contribute to the revenues of the Environmental Services operating segment. These services are generated from fees charged for waste material management and disposal services including onsite environmental management services, collection and transportation, packaging, recycling, treatment and disposal of waste. Revenue is primarily generated by short-term projects, most of which are governed by master service agreements that are long-term in nature. These master service agreements are typically entered into with the Company's larger customers and outline the pricing and legal frameworks for such arrangements. Services are provided based on purchase orders or agreements with the customer and include prices based upon units of volume of waste and transportation and other fees. Collection and transportation revenues are recognized

over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred as a basis for measuring the satisfaction of the performance obligation. Revenues for treatment and disposal of waste are recognized upon completion of treatment, final disposition in a landfill or incineration, or when the waste is shipped to a third party for processing and disposal. The Company periodically enters into bundled arrangements for the collection and transportation and disposal of waste. For such arrangements, transportation and disposal are considered distinct performance obligations and the Company allocates revenue to each based on the relative standalone selling price (i.e. the estimated price that a customer would pay for the services on a standalone basis). Revenues and the related costs from waste that is not yet completely processed and disposed of are deferred. The deferred revenues and costs are recognized when the services are completed. The period between collection and transportation and the final processing and disposal ranges depending on the location of the customer, but generally is measured in days.

Field and Emergency Response Services—Field and Emergency Response Services contribute to the revenues of the Environmental Services operating segment. Field Services revenues are generated from cleanup services at customer sites, including municipalities and utilities, or other locations on a scheduled or emergency response basis. Services include confined space entry for tank cleaning, site decontamination, large remediation projects, demolition, spill cleanup on land and water, railcar cleaning, product recovery and transfer and vacuum services. Additional services include filtration and water treatment services. Response services for environmental, contamination or pandemic related emergencies include any scale from man-made disasters such as oil spills to natural disasters such as hurricanes and more recently, projects involving contagion disinfection, decontamination and disposal services in response to the COVID-19 pandemic. Field and emergency response services are provided based on purchase orders or agreements with customers and include prices generally based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. The duration of such services can be over a number of hours, several days or even months for larger scale projects.

Industrial Services and Other—Industrial Services contribute to the revenues of the Environmental Services operating segment. These revenues are primarily generated from industrial and specialty services provided to refineries, mines, upgraders, chemical plants, pulp and paper mills, manufacturing facilities, power generation facilities and other industrial customers throughout North America. Services include in-plant cleaning and maintenance services, plant outage and turnaround services, specialty cleaning services including chemical cleaning and high and ultra-high pressure water cleaning, daylighting, production services and upstream energy services. Services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred.

Safety-Kleen Environmental Services—Safety-Kleen Environmental Services revenues contribute both to the Environmental Services operating segment and the Safety-Kleen Sustainability Solutions operating segment depending upon the nature of such revenues and operating responsibilities relative to satisfying the related performance obligations. Revenues from providing containerized waste handling and disposal services, parts washer services and vacuum services, referred to collectively as the Safety-Kleen Environmental core service offerings, contribute to the revenues of the Environmental Services operating segment. In addition, sales of packaged blended oil products and other complementary product sales contribute to the revenues of the Environmental Services operating segment. Revenues generated from waste oil, anti-freeze and oil filter collection services, sales of bulk blended oil products and sales of bulk automotive fluids contribute to the Safety-Kleen Sustainability Solutions operating segment.

Generally, the service related revenue is recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The duration of such services can be over a number of hours or several days. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Product revenue is recognized upon the transfer of control whereby control transfers when the products are delivered to the customer. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Related collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. Parts washer services include customer use of our parts washer equipment, cleaning and maintenance of the parts washer equipment and removal and replacement of used cleaning fluids. Parts washer services are considered a single performance obligation due to the highly integrated and interdependent nature of the arrangement. Revenue from parts washer services is recognized over the service interval as the customer receives the benefit of the services.

Safety-Kleen Oil—Safety-Kleen Oil revenues contribute to the revenues of the Safety-Kleen Sustainability Solutions segment. These revenues are generated from sales of high-quality base and blended lubricating oils to third-party distributors, government agencies, fleets, railroads and industrial customers. The business also sells recycled fuel oil to asphalt plants, industrial plants and pulp and paper companies. The used oil is also processed into vacuum gas oil which can be further re-refined into lubricant base oils or sold directly into the marine diesel oil fuel market. Revenue for oil products is recognized at a point in time, upon the transfer of control. Control transfers when the products are delivered to the customer.

Disaggregation of Revenue

We disaggregate the Company's third party revenues by geographic location and source of revenue as we believe these categories depict how revenue and cash flows are affected by economic factors (in thousands):


	For the Three Months Ended September 30, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	632,755	$	185,096	$	59	$	817,910
Canada	111,076		22,493		—		133,569
Total third-party revenues	$	743,831	$	207,589	$	59	$	951,479

Sources of Revenue
Technical Services	$	308,158	$	—	$	—	$	308,158
Field and Emergency Response Services	116,677		—		—		116,677
Industrial Services and Other	154,977		—		59		155,036
Safety-Kleen Environmental Services	164,019		39,551		—		203,570
Safety-Kleen Oil	—		168,038		—		168,038
Total third-party revenues	$	743,831	$	207,589	$	59	$	951,479


	For the Three Months Ended September 30, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	554,050	$	112,785	$	(186)	$	666,649
Canada	97,639		14,798		258		112,695
Total third-party revenues	$	651,689	$	127,583	$	72	$	779,344

Sources of Revenue
Technical Services	$	257,612	$	—	$	—	$	257,612
Field and Emergency Response Services	115,989		—		—		115,989
Industrial Services and Other	124,582		—		72		124,654
Safety-Kleen Environmental Services	153,506		49,949		—		203,455
Safety-Kleen Oil	—		77,634		—		77,634
Total third-party revenues	$	651,689	$	127,583	$	72	$	779,344


	For the Nine Months Ended September 30, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	1,824,848	$	504,302	$	217	$	2,329,367
Canada	295,008		61,710		—		356,718
Total third-party revenues	$	2,119,856	$	566,012	$	217	$	2,686,085

Sources of Revenue
Technical Services	$	887,063	$	—	$	—	$	887,063
Field and Emergency Response Services	328,831		—		—		328,831
Industrial Services and Other	425,154		—		217		425,371
Safety-Kleen Environmental Services	478,808		118,982		—		597,790
Safety-Kleen Oil	—		447,030		—		447,030
Total third-party revenues	$	2,119,856	$	566,012	$	217	$	2,686,085


	For the Nine Months Ended September 30, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	1,704,945	$	340,226	$	(648)	$	2,044,523
Canada	264,500		38,018		866		303,384
Total third-party revenues	$	1,969,445	$	378,244	$	218	$	2,347,907

Sources of Revenue
Technical Services	$	774,814	$	—	$	—	$	774,814
Field and Emergency Response Services	349,254		—		—		349,254
Industrial Services and Other	366,573		—		218		366,791
Safety-Kleen Environmental Services	478,804		134,004		—		612,808
Safety-Kleen Oil	—		244,240		—		244,240
Total third-party revenues	$	1,969,445	$	378,244	$	218	$	2,347,907

Contract Balances


(in thousands)	September 30, 2021		December 31, 2020
Receivables	$	703,199	$	611,534
Contract assets (unbilled receivables)	69,912		55,681
Contract liabilities (deferred revenue)	86,589		74,066

The timing of revenue recognition, billings and cash collections results in billed accounts receivable, unbilled receivables (contract assets) and customer advances and deposits or deferred revenue (contract liabilities) on the consolidated balance sheet. Generally, billing occurs subsequent to revenue recognition, as a right to payment is not just subject to passage of time, resulting in contract assets. Contract assets are classified as current. The Company sometimes receives advances or deposits from its customers before revenue is recognized, resulting in contract liabilities. These assets and liabilities are reported on the consolidated balance sheet on a contract-by-contract basis at the end of each reporting period. The contract liability balances at the beginning of each period presented were generally fully recognized in the subsequent three-month period.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

BUSINESS COMBINATIONS	9 Months Ended
BUSINESS COMBINATIONS	Sep. 30, 2021
Business Combination and Asset Acquisition [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS 2021 Acquisitions On March 27, 2021, the Company acquired a privately-owned business for $22.8 million cash consideration. The acquired company increases the Safety-Kleen Sustainability Solutions segment's network within the south central United States. In connection with this acquisition, a preliminary goodwill amount of $15.9 million was recognized. On October 8, 2021, the Company completed its previously announced proposed acquisition of LJ Energy Services Intermediate Holding Corp. and its subsidiaries (collectively, “HydroChemPSC”), a privately owned company. HydroChemPSC is a leading U.S. provider of industrial cleaning, specialty maintenance and utilities services with annual revenues of $715.3 million in 2020. The acquired operations, including more than 4,500 employees, over 240 service locations and a fleet of specialized vehicles and equipment, will enhance the Company's Environmental Services Segment. The Company paid an all-cash purchase price for HydroChemPSC of approximately $1.24 billion, subject to customary adjustments (e.g. working capital). The Company financed the purchase with the net proceeds of $983.0 million from the Company’s issuance of $1.0 billion of term loans on October 8, 2021. The remainder of the purchase price was funded through existing cash. See Note 11, "Financing Arrangements" for additional information regarding the issuance of the term loans. The acquisition of HydroChemPSC will be accounted for as a business combination and will be included in the Company's consolidated financial statements starting in periods after October 8, 2021. The allocation of the purchase price is incomplete due to the timing of the completion of the acquisition. Any excess of the purchase price over the fair value of the underlying tangible and identifiable intangible assets acquired and liabilities assumed will be recognized as goodwill. The Company believes that any goodwill recognized is primarily attributable to anticipated synergies, assembled workforce and new market opportunities that Clean Harbors believes will result from acquiring the operations of HydroChemPSC. Goodwill attributable to the acquisition of HydroChemPSC is preliminarily anticipated to range from 40% - 50% of the purchase price and is not expected to be deductible for tax purposes. On June 29, 2021, the Company signed a definitive agreement with Vertex Energy, Inc. ("Vertex") to acquire certain assets related to Vertex's used motor oil collection and re-refinery business in an all-cash transaction for $140.0 million, subject to working capital and other adjustments. The Company intends to fund the acquisition with available cash. The acquisition will include re-refineries in Marrero, Louisiana and Columbus, Ohio and service locations throughout the Midwest and Gulf Coast, as well as certain associated equipment and an assembled workforce. The acquisition was approved by Vertex shareholders on September 28, 2021; however, the transaction remains subject to approval by U.S. regulators and other customary closing conditions and is currently anticipated to close in 2022. The acquisition will expand the Safety-Kleen Sustainability Solutions segment's oil re-refining capacity and collection and distribution network. 2020 Acquisition On April 17, 2020, the Company acquired a privately-owned business for $8.8 million cash consideration. The acquired company expands the Safety-Kleen Sustainability Solutions segment's oil re-refining operations to the northeast United States. In connection with this acquisition, a goodwill amount of $1.4 million was recognized.

INVENTORIES AND SUPPLIES

9 Months Ended

Sep. 30, 2021

Inventory Disclosure [Abstract]

INVENTORIES AND SUPPLIES

Inventories and supplies consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Oil and oil related products	$	88,044	$	76,209
Supplies	119,953		120,007
Solvent and solutions	7,620		8,812
Other	13,065		15,470
Total inventories and supplies	$	228,682	$	220,498

Supplies consists primarily of critical spare parts to support the Company's incinerator and re-refinery operations, personal protective equipment and other general supplies used in our normal day-to-day operations. Other inventories consists primarily of parts washer components, cleaning fluids, absorbents and automotive fluids, such as windshield washer fluid and antifreeze.

PROPERTY, PLANT AND EQUIPMENT

9 Months Ended

Sep. 30, 2021

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Land	$	150,257	$	139,776
Asset retirement costs (non-landfill)	17,921		16,407
Landfill assets	200,545		191,687
Buildings and improvements (1)	524,397		509,804
Camp equipment	132,477		159,021
Vehicles (2)	864,808		844,026
Equipment (3)	1,821,327		1,807,235
Furniture and fixtures	6,838		7,082
Construction in progress	63,522		24,378
	3,782,092		3,699,416
Less - accumulated depreciation and amortization	2,273,736		2,174,118
Total property, plant and equipment, net	$	1,508,356	$	1,525,298

________________

(1) Balances inclusive of gross right-of-use ("ROU") assets classified as finance leases of $8.9 million in both periods.

(2) Balances inclusive of gross ROU assets classified as finance leases of $65.9 million and $47.2 million, respectively.

(3) Balances inclusive of gross ROU assets classified as finance leases of $9.3 million in both periods.

Depreciation expense, inclusive of landfill and finance lease amortization, was $63.9 million and $192.3 million for the three and nine months ended September 30, 2021, respectively. Depreciation expense, inclusive of landfill and finance lease amortization, was $64.9 million and $193.9 million for the three and nine months ended September 30, 2020, respectively.

GOODWILL AND OTHER INTANGIBLE ASSETS

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

The changes in goodwill by segment for the nine months ended September 30, 2021 were as follows (in thousands):


	Environmental Services		Safety-Kleen Sustainability Solutions		Totals
Balance at January 1, 2021	$	401,918	$	125,105	$	527,023
Increase from current period acquisition	—		15,860		15,860


Foreign currency translation	107		38		145
Balance at September 30, 2021	$	402,025	$	141,003	$	543,028

The balances in the table above have been recast to reflect the Company's segment change in the first quarter of 2021. As discussed in Note 17, "Segment Reporting," as a result of operational and managerial changes, the Company changed its operating segments in accordance with ASC 280, Segment Reporting. In addition, the Company concluded that, for purposes of reviewing for potential goodwill impairment, it now has three reporting units. The Environmental Services operating segment has two reporting units consisting of (i) Environmental Sales and Service which includes the legacy Environmental Sales and Service reporting unit and certain operations previously included within Safety-Kleen Environmental Services including the core service offerings of containerized waste, parts washer and vacuum services and (ii) Environmental Facilities, unchanged from prior year. The Safety-Kleen Sustainability Solutions operating segment is a single reporting unit which includes the legacy Safety-Kleen Oil reporting unit and the remaining operations of the legacy Safety-Kleen Environmental Services reporting unit primarily consisting of collection services for waste oil, anti-freeze and used oil filters as well as the sale of bulk blended re-refined oil and other automotive related finished fluid products. The Company allocated goodwill to the newly identified reporting units using a relative fair value approach. In addition, the Company completed an assessment of any potential goodwill impairment for all reporting units immediately prior and subsequent to the reallocation and determined that no impairment existed.

As of September 30, 2021 and December 31, 2020, the Company's intangible assets consisted of the following (in thousands):


	September 30, 2021						December 31, 2020
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	186,334	$	100,553	$	85,781	$	183,766	$	95,033	$	88,733
Customer and supplier relationships	361,438		207,497		153,941		382,083		211,895		170,188
Other intangible assets	20,388		16,795		3,593		39,287		34,744		4,543
Total amortizable permits and other intangible assets	568,160		324,845		243,315		605,136		341,672		263,464
Trademarks and trade names	123,182		—		123,182		123,156		—		123,156
Total permits and other intangible assets	$	691,342	$	324,845	$	366,497	$	728,292	$	341,672	$	386,620

Amortization expense of permits, customer and supplier relationships and other intangible assets was $7.6 million and $22.9 million in the three and nine months ended September 30, 2021, respectively. Amortization expense of permits, customer and supplier relationships and other intangible assets was $9.6 million and $27.6 million in the three and nine months ended September 30, 2020, respectively. The gross cost and accumulated amortization decreases in total amortizable permits and other intangible assets are attributable to writing off fully amortized intangible assets with a cost of $39.7 million during the nine months ended September 30, 2021.

The expected amortization of the net carrying amount of finite-lived intangible assets at September 30, 2021 was as follows (in thousands):


Years Ending December 31,	Expected Amortization
2021 (three months)	$	7,526
2022	30,002
2023	25,674
2024	24,180
2025	23,208
Thereafter	132,725
	$	243,315

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

9 Months Ended

Sep. 30, 2021

Payables and Accruals [Abstract]

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

Accrued expenses and other current liabilities consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Accrued insurance	$	80,072	$	77,514
Accrued interest	9,281		19,697
Accrued compensation and benefits	94,256		81,437
Accrued income, real estate, sales and other taxes	29,629		25,843
Interest rate swap liability	23,496		33,630
Accrued other	62,693		57,702
	$	299,427	$	295,823

CLOSURE AND POST-CLOSURE LIABILITIES

9 Months Ended

Sep. 30, 2021

Asset Retirement Obligation Disclosure [Abstract]

CLOSURE AND POST-CLOSURE LIABILITIES

The changes to closure and post-closure liabilities (also referred to as “asset retirement obligations”) from January 1, 2021 through September 30, 2021 were as follows (in thousands):


	Landfill Retirement Liability		Non-Landfill Retirement Liability		Total
Balance at January 1, 2021	$	48,412	$	39,514	$	87,926
Liabilities assumed in acquisitions	—		451		451

New asset retirement obligations	1,979		—		1,979

Accretion	2,600		2,744		5,344
Changes in estimates recorded to consolidated statement of operations	35		291		326
Changes in estimates recorded to consolidated balance sheet	668		1,226		1,894
Expenditures	(4,420)		(461)		(4,881)
Currency translation and other	—		(11)		(11)
Balance at September 30, 2021	$	49,274	$	43,754	$	93,028

In the nine months ended September 30, 2021, there were no significant charges (benefits) resulting from changes in estimates for closure and post-closure liabilities.

New asset retirement obligations incurred during the first nine months of 2021 were discounted at the credit-adjusted risk-free rate of 4.84%.

REMEDIAL LIABILITIES

9 Months Ended

Sep. 30, 2021

Environmental Remediation Obligations [Abstract]

REMEDIAL LIABILITIES

The changes to remedial liabilities from January 1, 2021 through September 30, 2021 were as follows (in thousands):


	Remedial Liabilities for Landfill Sites		Remedial Liabilities for Inactive Sites		Remedial Liabilities (Including Superfund) for Non-Landfill Operations		Total
Balance at January 1, 2021	$	1,865	$	63,060	$	49,888	$	114,813


Accretion	67		1,955		1,259		3,281
Changes in estimates recorded to consolidated statement of operations	(22)		358		(321)		15
Expenditures	(37)		(3,963)		(3,342)		(7,342)
Currency translation and other	—		(821)		870		49
Balance at September 30, 2021	$	1,873	$	60,589	$	48,354	$	110,816

In the nine months ended September 30, 2021, there were no significant (benefits) charges resulting from changes in estimates for remedial liabilities.

FINANCING ARRANGEMENTS

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

FINANCING ARRANGEMENTS

The following table is a summary of the Company’s financing arrangements (in thousands):


Current Debt:	September 30, 2021		December 31, 2020
Secured senior term loans	$	7,535	$	7,535

Long-Term Debt:
Secured senior term loans due June 30, 2024 ("2024 Term Loans")	$	713,975	$	719,626
Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")	545,000		545,000
Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")	300,000		300,000
Long-term debt, at par	$	1,558,975	$	1,564,626
Unamortized debt issuance costs and premium, net	(12,691)		(14,985)
Long-term debt, at carrying value	$	1,546,284	$	1,549,641

Financing Activities

As of September 30, 2021 and December 31, 2020, the estimated fair value of the Company’s outstanding long-term debt, including the current portion, was $1.6 billion. The Company’s estimates of fair value of its long-term debt, including the current portion, are based on quoted market prices or other available market data which are considered Level 2 measures according to the fair value hierarchy. Level 2 utilizes quoted market prices in markets that are not active, broker or dealer quotations or alternative pricing sources with reasonable levels of price transparency for similar assets and liabilities.

The Company maintains a $400.0 million revolving credit facility under which the Company had no outstanding loan balances as of September 30, 2021 and December 31, 2020. As of September 30, 2021, the Company had $288.5 million available to borrow under the revolving credit facility and outstanding letters of credit were $111.5 million. This credit facility will expire in October 2025.

On October 8, 2021, the Company, and substantially all of the Company’s domestic subsidiaries as guarantors, entered into Incremental Facility Amendment No. 2 to the Company’s existing Credit Agreement dated as of June 30, 2017 (the “Term Loan Agreement”). Incremental Facility Amendment No. 2 provides for a new class and series of Term Loans (the “2028 Term Loans”) in the aggregate principal amount of $1.0 billion. Proceeds from the issuance of the 2028 Term Loans were $983.0 million, after debt discount and debt issuance costs and were used to fund the acquisition of HydroChemPSC on October 8, 2021. The 2028 Term Loans are in addition to the aggregate of $721.5 million of 2024 Term Loans which were at September 30, 2021 and are also outstanding under the Term Loan Agreement and which will mature on June 30, 2024. The 2028 Term Loans will mature on October 8, 2028, and may be prepaid at any time without premium or penalty other than customary breakage costs with respect to Eurodollar based loans or if the Company engages in certain repricing transactions before May 9, 2022, in which event a 1.0% prepayment premium would be due. The Company’s obligations under the Term Loan Agreement with respect to both the 2024 Term Loans and the 2028 Term Loans are guaranteed by all of the Company’s domestic restricted subsidiaries and secured by liens on substantially all of the assets of the Company and the guarantors.

The 2028 Term Loans under the Term Loan Agreement bear interest, at the Company’s election, at either of the following rates: (a) the sum of the Eurodollar Rate (as defined in the Term Loan Agreement) plus 2.00%, or (b) the sum of the Base Rate (as defined in the Term Loan Agreement) plus 1.00%, with the Eurodollar Rate being subject to a floor of 0.00% and the Base Rate being subject to a floor of 1.00%.

Cash Flow Hedges

The Company’s strategy to hedge against fluctuations in variable interest rates involves entering into interest rate derivative agreements. Although the interest rates on the 2024 Term Loans and the 2028 Term Loans are variable, the Company has effectively fixed the interest rate on $350.0 million aggregate principal amount of the 2024 Term Loans outstanding by entering into interest rate swap agreements in 2018 with a notional amount of $350.0 million. Under the terms of the interest rate swap agreements, the Company receives interest based on the one-month LIBOR index and pays interest at a weighted average annual interest rate of 2.92%, resulting in an effective annual interest rate of 4.67%. The interest rate swap agreements terminate in 2024.

The Company recognizes derivative instruments as either assets or liabilities on the balance sheet at fair value. No ineffectiveness has been identified on these swaps and, therefore, all unrealized changes in fair value are recorded in accumulated other comprehensive loss. Amounts are reclassified from accumulated other comprehensive loss into interest expense on the statement of operations in the same period or periods during which the hedged transaction affects earnings.

As of September 30, 2021 and December 31, 2020, the Company has recorded a derivative liability with a fair value of $23.5 million and $33.6 million, respectively, within accrued expenses and other current liabilities in connection with these cash flow hedges.

The fair value of the interest rate swaps is calculated using discounted cash flow valuation methodologies based upon the one-month LIBOR yield curves that are observable at commonly quoted intervals for the full term of the interest rate swaps and as such is considered a Level 2 measure according to the fair value hierarchy.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

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+ Details

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company records a tax provision or benefit on an interim basis using an estimated annual effective tax rate. This rate is applied to the current period ordinary income or loss to determine the income tax provision or benefit allocated to the interim period. Losses from jurisdictions for which no benefit can be recognized and the income tax effects of unusual or infrequent items are excluded from the estimated annual effective tax rate and are recognized in the impacted interim period. The estimated annual effective tax rate may be significantly impacted by projected earnings mix by tax jurisdiction. Adjustments to the estimated annual effective income tax rate are recognized in the period when such estimates are revised. The Company’s effective tax rate for the three and nine months ended September 30, 2021 was 24.8% and 26.3%, compared to 20.0% and 27.0%, respectively, for the comparable periods in 2020. As of September 30, 2021 and December 31, 2020, the Company had recorded $5.4 million and $5.5 million, respectively, of gross liabilities for unrecognized tax benefits and $2.2 million and $2.1 million, respectively, of accrued interest.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

EARNINGS PER SHARE

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

EARNINGS PER SHARE

The following are computations of basic and diluted earnings per share (in thousands, except per share amounts):


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
Numerator for basic and diluted earnings per share:
Net income	$	65,443	$	54,910	$	154,254	$	95,505

Denominator:
Basic shares outstanding	54,411		55,592		54,553		55,646
Dilutive effect of outstanding stock awards	296		146		309		186
Dilutive shares outstanding	54,707		55,738		54,862		55,832

Basic earnings per share:	$	1.20	$	0.99	$	2.83	$	1.72

Diluted earnings per share:	$	1.20	$	0.99	$	2.81	$	1.71

For the three months ended September 30, 2021 and September 30, 2020, all then outstanding performance awards and restricted stock awards were included in the calculation of diluted earnings per share except for 67,019 and 235,806, respectively, of performance stock awards for which the performance criteria were not attained at the reporting dates and 38,250 and 16,183, respectively, of restricted stock awards which were excluded as their inclusion would have an antidilutive effect.

For the nine months ended September 30, 2021 and September 30, 2020, all then outstanding performance awards and restricted stock awards were included in the calculation of diluted earnings per share except for 67,019 and 235,806, respectively, of performance stock awards for which the performance criteria were not attained at the reporting dates and 39,750 and 14,516, respectively, of restricted stock awards which were excluded as their inclusion would have an antidilutive effect.

ACCUMULATED OTHER COMPREHENSIVE LOSS

9 Months Ended

Sep. 30, 2021

Equity [Abstract]

ACCUMULATED OTHER COMPREHENSIVE LOSS

The changes in accumulated other comprehensive loss by component and related tax impacts for the nine months ended September 30, 2021 were as follows (in thousands):


	Foreign Currency Translation		Unrealized Gains (Losses) on Available-For-Sale Securities		Unrealized (Losses) Gains on Interest Rate Hedge		Unrealized Losses on Unfunded Pension Liability		Total
Balance at January 1, 2021	$	(176,234)	$	135	$	(33,629)	$	(1,749)	$	(211,477)
Other comprehensive income (loss) before reclassifications	767		(177)		2,660		—		3,250
Amounts reclassified out of accumulated other comprehensive loss	—		—		7,474		—		7,474
Tax benefit	—		37		—		—		37
Other comprehensive income (loss)	767		(140)		10,134		—		10,761
Balance at September 30, 2021	$	(175,467)	$	(5)	$	(23,495)	$	(1,749)	$	(200,716)

The amount reclassified out of accumulated other comprehensive loss into the consolidated statement of operations, with presentation location, during the three and nine months ended September 30, 2021 was as follows (in thousands):


Other Comprehensive Income (Loss) Component	For the Three Months Ended September 30, 2021		For the Nine Months Ended September 30, 2021		Location

Unrealized losses on interest rate hedge	$	(2,532)	$	(7,474)	Interest expense, net of interest income

STOCK-BASED COMPENSATION

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

Total stock-based compensation cost charged to selling, general and administrative expenses for the three and nine months ended September 30, 2021 was $6.0 million and $12.8 million, respectively. Total stock-based compensation cost charged to selling, general and administrative expenses for the three and nine months ended September 30, 2020 was $6.7 million and $12.7 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense for the three and nine months ended September 30, 2021 was $1.3 million and $2.8 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense for the three and nine months ended September 30, 2020 was $1.7 million and $2.9 million, respectively.

Restricted Stock Awards

The following table summarizes information about restricted stock awards for the nine months ended September 30, 2021:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2021	493,879	$	59.74
Granted	174,225	93.95
Vested	(181,651)	57.68
Forfeited	(39,091)	61.75
Balance at September 30, 2021	447,362	73.72

As of September 30, 2021, there was $26.3 million of total unrecognized compensation cost arising from restricted stock awards. This cost is expected to be recognized over a weighted average period of 3.0 years. The total fair value of restricted stock vested during the three and nine months ended September 30, 2021 was $7.4 million and $16.3 million, respectively. The total fair value of restricted stock vested during the three and nine months ended September 30, 2020 was $3.1 million and $12.8 million, respectively.

Performance Stock Awards

Performance stock awards are subject to performance criteria established by the Compensation Committee of the Company's Board of Directors prior to or at the date of grant. The vesting of the performance stock awards is based on achieving targets currently based on revenue, Adjusted EBITDA, Adjusted EBITDA Margin, Adjusted Free Cash Flow, Return on Invested Capital and Total Recordable Incident Rate. In addition, performance stock awards include continued service conditions.

The following table summarizes information about performance stock awards for the nine months ended September 30, 2021:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2021	254,449	$	61.75
Granted	134,931	92.92
Vested	(71,815)	62.27
Forfeited	(26,191)	64.47
Balance at September 30, 2021	291,374	75.81

As of September 30, 2021, there was $10.0 million of total unrecognized compensation cost arising from unvested performance stock awards deemed probable of vesting. No performance awards vested during the three months ended September 30, 2021 and September 30, 2020. The total fair value of performance awards vested during the nine months ended September 30, 2021 and September 30, 2020 was $6.4 million and $1.3 million, respectively.

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal and Administrative Proceedings The Company and its subsidiaries are subject to legal proceedings and claims arising in the ordinary course of business. Actions filed against the Company arise from commercial and employment-related claims including alleged class actions related to sales practices and wage and hour claims. The plaintiffs in these actions may be seeking damages or injunctive relief or both. These actions are in various jurisdictions and stages of proceedings, and some are covered in part by insurance. In addition, the Company’s waste management services operations are regulated by federal, state, provincial and local laws enacted to regulate discharge of materials into the environment, remediation of contaminated soil and groundwater or otherwise protect the environment. This ongoing regulation results in the Company frequently becoming a party to legal or administrative proceedings involving all levels of governmental authorities and other interested parties. The issues involved in such proceedings generally relate to alleged violations of existing permits and licenses or alleged responsibility under federal or state Superfund laws to remediate contamination at properties owned either by the Company or by other parties (“third-party sites”) to which either the Company or the prior owners of certain of the Company’s facilities shipped waste. At September 30, 2021 and December 31, 2020, the Company had recorded reserves of $30.4 million and $29.8 million, respectively, in the Company's financial statements for actual or probable liabilities related to the legal and administrative proceedings in which the Company was then involved, the principal of which are described below. In management's opinion, it is not reasonably possible that the potential liability beyond what has been recorded, if any, that may result from these actions, either individually or collectively, will have a material effect on our financial position, results of operations or cash flows. The Company periodically adjusts the aggregate amount of these reserves when actual or probable liabilities are paid or otherwise discharged, new claims arise or additional relevant information about existing or probable claims becomes available. As of September 30, 2021 and December 31, 2020, the $30.4 million and $29.8 million, respectively, of reserves consisted of (i) $23.2 million and $24.0 million, respectively, related to pending legal or administrative proceedings, including Superfund liabilities, which were included in remedial liabilities on the consolidated balance sheets, and (ii) $7.2 million and $5.8 million, respectively, primarily related to federal, state and provincial enforcement actions, which were included in accrued expenses and other current liabilities on the consolidated balance sheets. As of September 30, 2021, the Company's principal legal and administrative proceedings were as follows: Ville Mercier. In September 2002, the Company acquired the stock of a subsidiary (the "Mercier Subsidiary") which owns a hazardous waste incinerator in Ville Mercier, Quebec (the "Mercier Facility"). The property adjacent to the Mercier Facility, which is also owned by the Mercier Subsidiary, is now contaminated as a result of actions dating back to 1968, when the Government of Quebec issued two permits to dump organic liquids into lagoons on the property to a company unrelated to the Mercier Subsidiary. In 1999, Ville Mercier and three neighboring municipalities filed separate legal proceedings against the Mercier Subsidiary and the Government of Quebec. In 2012, the municipalities amended their existing statement of claim to seek $2.9 million (CAD) in general damages and $10.0 million (CAD) in punitive damages, plus interest and costs, as well as injunctive relief. Both the Government of Quebec and the Company have filed summary judgment motions against the municipalities. The parties are attempting to negotiate a resolution and hearings on the motions have been delayed. In September 2007, the Quebec Minister of Sustainable Development, Environment and Parks issued a notice pursuant to Section 115.1 of the Environment Quality Act, superseding notices issued in 1992, which are the subject of the pending litigation. The more recent notice notifies the Mercier Subsidiary that, if the Mercier Subsidiary does not take certain remedial measures at the site, the Minister intends to undertake those measures at the site and claim direct and indirect costs related to such measures. The Company has accrued for costs expected to be incurred relative to the resolution of this matter and believes this matter will not have future material effect on its financial position, results of operations or cash flows. Safety-Kleen Legal Proceedings. On December 28, 2012, the Company acquired Safety-Kleen, Inc. ("Safety-Kleen") and thereby became subject to the legal proceedings in which Safety-Kleen was a party on that date. In addition to certain Superfund proceedings in which Safety-Kleen has been named as a potentially responsible party as described below under “Superfund Proceedings,” the principal such legal proceedings involving Safety-Kleen which were outstanding as of September 30, 2021 were as follows: Product Liability Cases. Safety-Kleen has been named as a defendant in various lawsuits that are currently pending in various courts and jurisdictions throughout the United States, including approximately 69 proceedings (excluding cases which have been settled but not formally dismissed) as of September 30, 2021, wherein persons claim personal injury resulting from the use of Safety-Kleen's parts washer equipment or cleaning products. These proceedings typically involve allegations that the solvent used in Safety-Kleen's parts washer equipment contains contaminants and/or that Safety-Kleen's recycling process does not effectively remove the contaminants that become entrained in the solvent during their use. In addition, certain claimants assert that Safety-Kleen failed to adequately warn the product user of potential risks, including a historic failure to warn that solvent contains trace amounts of toxic or hazardous substances such as benzene. The Company maintains insurance that it believes will provide coverage for these product liability claims (over amounts accrued for self-insured retentions and deductibles in certain limited cases), except for punitive damages to the extent not insurable under state law or excluded from insurance coverage. The Company also believes that these claims lack merit and has historically vigorously defended, and intends to continue to vigorously defend, itself and the safety of its products against all these claims. Such matters are subject to many uncertainties and outcomes are not predictable with assurance. Consequently, the Company is unable to ascertain the ultimate aggregate amount of monetary liability or financial impact with respect to these matters as of September 30, 2021. From January 1, 2021 to September 30, 2021, 12 product liability claims were settled or dismissed. Due to the nature of these claims and the related insurance, the Company did not incur any expense as insurance provided coverage in full for all such claims. Safety-Kleen may be named in similar, additional lawsuits in the future, including claims for which insurance coverage may not be available. Superfund Proceedings The Company has been notified that either the Company or the prior owners of certain of the Company's facilities for which the Company may have certain indemnification obligations have been identified as potentially responsible parties ("PRPs") or potential PRPs in connection with 131 sites which are subject to or are proposed to become subject to proceedings under federal or state Superfund laws. Of the 131 Superfund related sites, six (including the BR Facility described below) involve facilities that are now owned or leased by the Company and 125 involve third-party sites to which either the Company or the prior owners of certain of the Company’s facilities shipped wastes. Of the 125 third-party sites, 30 are now settled, 15 are currently requiring expenditures on remediation and 80 are not currently requiring expenditures on remediation. In connection with each site, the Company has estimated the extent, if any, to which it may be subject, either directly or as a result of any indemnification obligations, for cleanup and remediation costs, related legal and consulting costs associated with PRP investigations, settlements and related legal and administrative proceedings. The amount of such actual and potential liability is inherently difficult to estimate because of, among other relevant factors, uncertainties as to the legal liability, if any, of the Company or the prior owners of certain of the Company's facilities to contribute a portion of the cleanup costs, the assumptions that must be made in calculating the estimated cost and timing of remediation, the identification of other PRPs and their respective capability and obligation to contribute to remediation efforts and the existence and legal standing of indemnification agreements, if any, with prior owners, which may either benefit the Company or subject the Company to potential indemnification obligations. The Company believes its potential liability could exceed $1.0 million at three of the 131 Superfund related sites. BR Facility. The Company acquired in 2002 a former hazardous waste incinerator and landfill in Baton Rouge (the "BR Facility"), for which operations had been previously discontinued by the prior owner. In September 2007, the U.S. Environmental Protection Agency ("EPA") issued a special notice letter to the Company related to the Devil's Swamp Lake Site ("Devil's Swamp") in East Baton Rouge Parish, Louisiana. Devil's Swamp includes a lake located downstream of an outfall ditch where wastewater and storm water have been discharged, and Devil's Swamp is proposed to be included on the National Priorities List due to the presence of Contaminants of Concern ("COC") cited by the EPA. These COCs include substances of the kind found in wastewater and storm water discharged from the BR Facility in past operations. The EPA originally requested COC generators to submit a good faith offer to conduct a remedial investigation feasibility study directed towards the eventual remediation of the site. In 2018, the Company completed performing corrective actions at the BR Facility under an order issued by the Louisiana Department of Environmental Quality and has also completed conducting the remedial investigation feasibility study for Devil's Swamp under the order issued by the EPA at which point the feasibility study, with several remedial alternatives, was submitted to the EPA for review. During 2020, the EPA signed a Record of Decision which defined the remediation alternative selected and approved by the EPA and in return, the Company increased the estimated remedial liability for this inactive site by $3.3 million. Changes in the natural landscape and/or new information identified during the remediation could impact this estimate; however, any such changes are not expected to have a future material effect on the Company's financial position, liquidity or results of operation. Third-Party Sites. Of the 125 third-party Superfund sites at which the Company has been notified it is a PRP or potential PRP or may have indemnification obligations, the Company has an indemnification agreement at a total of 18 sites. These agreements indemnify the Company (which now includes Safety-Kleen) with respect to any liability at the 18 sites for waste disposed prior to the Company's (or Safety-Kleen's) acquisition of the former subsidiaries of Waste Management, McKesson and one other entity which had shipped wastes to those sites. Accordingly, the indemnifying parties are paying all costs of defending those subsidiaries in those 18 cases, including legal fees and settlement costs. However, there can be no guarantee that the Company's ultimate liabilities for those sites will not exceed the amount recorded or that indemnities applicable to any of these sites will be available to pay all or a portion of related costs. Except for the indemnification agreements which the Company holds from ChemWaste, McKesson and one other entity, the Company does not have an indemnity agreement with respect to any of the 125 third-party sites discussed above. Federal, State and Provincial Enforcement Actions From time to time, the Company pays fines or penalties in regulatory proceedings relating primarily to waste treatment, storage or disposal facilities. As of September 30, 2021 there was one proceeding for which the Company reasonably believes that the sanctions could equal or exceed $1.0 million, and none as of December 31, 2020. The Company believes that the fines or other penalties in these or any of the other regulatory proceedings will not, individually or in the aggregate, have a material effect on its financial condition, results of operations or cash flows.

SEGMENT REPORTING

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

SEGMENT REPORTING

Segment reporting is prepared on the same basis that the Company's chief executive officer, who is the Company's chief operating decision maker, manages the business, makes operating decisions and assesses performance. As described in the "Changes in Operating Segments" section of Note 2, "Significant Accounting Policies," during the first quarter of 2021, certain of the Company's businesses undertook a reorganization which included changes to the underlying business and management structures. The Company's chief operating decision maker also requested changes in the information that he regularly reviews for purposes of allocating resources and assessing performance so that the information would align with the new operating structure of the business. Due to these changes the Company reassessed its operating segment conclusions in the first quarter of 2021 which resulted in a change in the operating segments. The Company consolidated the core services of Safety-Kleen Environmental Services into its Environmental Services segment, eliminated its Safety-Kleen segment and created the Safety-Kleen Sustainability Solutions segment. In addition, certain intercompany transactions previously recorded as Corporate Items have been allocated to the segments. All the historical balances presented below have been recast to reflect the impact of these changes.

Third-party revenue is revenue billed to outside customers by a particular segment. Direct revenues is revenue allocated to the segment providing the product or service. Intersegment revenues represent the sharing of third-party revenues among the segments based on products and services provided by each segment as if the products and services were sold directly to the third-party. Transactions between the segments are accounted for at the Company’s best estimate based on similar transactions with

outside customers. The intersegment revenues are shown net. The operations not managed through the Company’s operating segments described above are recorded as “Corporate Items.”

The following table reconciles third-party revenues to direct revenues for the three and nine months ended September 30, 2021 and September 30, 2020 (in thousands):


	For the Three Months Ended September 30, 2021				For the Three Months Ended September 30, 2020
	Third-party revenues		Intersegment revenues, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Direct revenues
Environmental Services	$	743,831	$	1,802	$	745,633	$	651,689	$	(1,129)	$	650,560
Safety-Kleen Sustainability Solutions	207,589		(1,802)		205,787		127,583		1,129		128,712
Corporate Items	59		—		59		72		—		72
Total	$	951,479	$	—	$	951,479	$	779,344	$	—	$	779,344


	For the Nine Months Ended September 30, 2021				For the Nine Months Ended September 30, 2020
	Third-party revenues		Intersegment revenues, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Direct revenues
Environmental Services	$	2,119,856	$	4,476	$	2,124,332	$	1,969,445	$	(1,099)	$	1,968,346
Safety-Kleen Sustainability Solutions	566,012		(4,476)		561,536		378,244		1,099		379,343
Corporate Items	217		—		217		218		—		218
Total	$	2,686,085	$	—	$	2,686,085	$	2,347,907	$	—	$	2,347,907

The primary financial measure by which the Company evaluates the performance of its segments is "Adjusted EBITDA," which consists of net income plus accretion of environmental liabilities, stock-based compensation, depreciation and amortization, net interest expense, loss on early extinguishment of debt, provision for income taxes and excludes other gains, losses or non-cash charges not deemed representative of fundamental segment results and other expense, net. Beginning in the first quarter of 2021, we revised our calculation of reported Adjusted EBITDA to add stock-based compensation, a non-cash item, to other charges which are added back to net income determined in accordance with generally accepted accounting principles ("GAAP") for purposes of calculating Adjusted EBITDA. The amount added back each period matches the line item for stock-based compensation as recorded on the consolidated statements of cash flows. All relevant prior period Adjusted EBITDA amounts were recast to provide comparative information.

The following table presents Adjusted EBITDA information used by management by reported segment (in thousands):


	For the Three Months Ended				For the Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
Adjusted EBITDA:
Environmental Services	$	166,471	$	180,002	$	482,766	$	502,101
Safety-Kleen Sustainability Solutions	70,810		29,613		165,756		62,248
Corporate Items	(52,197)		(41,782)		(146,216)		(132,369)
Total	185,084		167,833		502,306		431,980
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,799		2,822		8,625		8,149
Stock-based compensation	6,001		6,662		12,786		12,739
Depreciation and amortization	71,451		74,470		215,206		221,497
Income from operations	104,833		83,879		265,689		189,595
Other (income) expense, net	(199)		(2,268)		2,509		597
Loss on sale of businesses	—		118		—		3,376

Interest expense, net of interest income	17,984		17,407		53,953		54,848
Income before provision for income taxes	$	87,048	$	68,622	$	209,227	$	130,774

The following table presents certain assets by reportable segment and in the aggregate (in thousands):


	September 30, 2021		December 31, 2020
Property, plant and equipment, net:
Environmental Services	$	1,050,901	$	1,068,910
Safety-Kleen Sustainability Solutions	363,857		366,160
Corporate Items	93,598		90,228
Total property, plant and equipment, net	$	1,508,356	$	1,525,298

Goodwill and Permits and other intangibles, net:
Environmental Services
Goodwill	$	402,025	$	401,918
Permits and other intangibles, net	217,188		228,237
Total Environmental Services	619,213		630,155

Safety-Kleen Sustainability Solutions
Goodwill	$	141,003	$	125,105
Permits and other intangibles, net	149,309		158,383
Total Safety-Kleen Sustainability Solutions	290,312		283,488

Total	$	909,525	$	913,643

The following table presents the total assets by geographical area (in thousands):


	September 30, 2021		December 31, 2020
United States	$	3,629,056	$	3,447,811
Canada and other foreign	725,243		683,709
Total	$	4,354,299	$	4,131,520

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2021
Accounting Policies [Abstract]
Changes in Operating Segments	During the first quarter of 2021, the Company reorganized its Safety-Kleen business. The collection services for waste oil, used oil filters, antifreeze and related items and bulk blended oil sales operations were combined with the Safety-Kleen Oil business to form the Safety-Kleen Sustainability Solutions business. Under this structure, Safety-Kleen Sustainability Solutions will encompass both sides of the spread the Company manages in its re-refinery business, and the Company expects this change to drive additional growth in its sustainable lubricant products and related services. Concurrently with this change, the Company consolidated the Safety-Kleen Environmental branches' core offerings, including containerized waste, parts washer and vacuum services, into the legacy Clean Harbors Environmental Services sales and service operations. The Company expects this change to foster enhanced cross-selling opportunities within the environmental businesses and increase market presence with small quantity generators of hazardous waste. In restructuring the operations of the Company in this manner, the information that the chief operating decision maker regularly reviews for purposes of allocating resources and assessing performance changed to conform to this new operating structure of the business and the Company reevaluated the identification of its operating segments. In accordance with ASC 280, Segment Reporting, Environmental Services and Safety-Kleen Sustainability Solutions are the Company's operating segments and reportable segments starting in the first quarter of 2021, with the operations not managed through the Company's operating segments described above continuing to be recorded as Corporate Items. See Note 17, "Segment Reporting" for more information. The amounts presented for the three and nine months ended September 30, 2020 and any segment information presented as of December 31, 2020 have been recast to reflect the impact of such changes. In addition, certain intercompany transactions previously recorded in Corporate Items have been allocated to the segments. These reclassifications and adjustments had no effect on the consolidated statements of operations, consolidated statements of comprehensive income (loss), consolidated statements of cash flows or consolidated statements of stockholders' equity for any of the periods presented.
Revenue recognition	The Company generates revenues through its Environmental Services and Safety-Kleen Sustainability Solutions operating segments. The Company's Environmental Services operating segment has four sources of revenue and the Safety-Kleen Sustainability Solutions operating segment has two sources of revenue. Technical Services—Technical Services contribute to the revenues of the Environmental Services operating segment. These services are generated from fees charged for waste material management and disposal services including onsite environmental management services, collection and transportation, packaging, recycling, treatment and disposal of waste. Revenue is primarily generated by short-term projects, most of which are governed by master service agreements that are long-term in nature. These master service agreements are typically entered into with the Company's larger customers and outline the pricing and legal frameworks for such arrangements. Services are provided based on purchase orders or agreements with the customer and include prices based upon units of volume of waste and transportation and other fees. Collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred as a basis for measuring the satisfaction of the performance obligation. Revenues for treatment and disposal of waste are recognized upon completion of treatment, final disposition in a landfill or incineration, or when the waste is shipped to a third party for processing and disposal. The Company periodically enters into bundled arrangements for the collection and transportation and disposal of waste. For such arrangements, transportation and disposal are considered distinct performance obligations and the Company allocates revenue to each based on the relative standalone selling price (i.e. the estimated price that a customer would pay for the services on a standalone basis). Revenues and the related costs from waste that is not yet completely processed and disposed of are deferred. The deferred revenues and costs are recognized when the services are completed. The period between collection and transportation and the final processing and disposal ranges depending on the location of the customer, but generally is measured in days. Field and Emergency Response Services—Field and Emergency Response Services contribute to the revenues of the Environmental Services operating segment. Field Services revenues are generated from cleanup services at customer sites, including municipalities and utilities, or other locations on a scheduled or emergency response basis. Services include confined space entry for tank cleaning, site decontamination, large remediation projects, demolition, spill cleanup on land and water, railcar cleaning, product recovery and transfer and vacuum services. Additional services include filtration and water treatment services. Response services for environmental, contamination or pandemic related emergencies include any scale from man-made disasters such as oil spills to natural disasters such as hurricanes and more recently, projects involving contagion disinfection, decontamination and disposal services in response to the COVID-19 pandemic. Field and emergency response services are provided based on purchase orders or agreements with customers and include prices generally based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. The duration of such services can be over a number of hours, several days or even months for larger scale projects. Industrial Services and Other—Industrial Services contribute to the revenues of the Environmental Services operating segment. These revenues are primarily generated from industrial and specialty services provided to refineries, mines, upgraders, chemical plants, pulp and paper mills, manufacturing facilities, power generation facilities and other industrial customers throughout North America. Services include in-plant cleaning and maintenance services, plant outage and turnaround services, specialty cleaning services including chemical cleaning and high and ultra-high pressure water cleaning, daylighting, production services and upstream energy services. Services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Safety-Kleen Environmental Services—Safety-Kleen Environmental Services revenues contribute both to the Environmental Services operating segment and the Safety-Kleen Sustainability Solutions operating segment depending upon the nature of such revenues and operating responsibilities relative to satisfying the related performance obligations. Revenues from providing containerized waste handling and disposal services, parts washer services and vacuum services, referred to collectively as the Safety-Kleen Environmental core service offerings, contribute to the revenues of the Environmental Services operating segment. In addition, sales of packaged blended oil products and other complementary product sales contribute to the revenues of the Environmental Services operating segment. Revenues generated from waste oil, anti-freeze and oil filter collection services, sales of bulk blended oil products and sales of bulk automotive fluids contribute to the Safety-Kleen Sustainability Solutions operating segment. Generally, the service related revenue is recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The duration of such services can be over a number of hours or several days. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Product revenue is recognized upon the transfer of control whereby control transfers when the products are delivered to the customer. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Related collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. Parts washer services include customer use of our parts washer equipment, cleaning and maintenance of the parts washer equipment and removal and replacement of used cleaning fluids. Parts washer services are considered a single performance obligation due to the highly integrated and interdependent nature of the arrangement. Revenue from parts washer services is recognized over the service interval as the customer receives the benefit of the services. Safety-Kleen Oil—Safety-Kleen Oil revenues contribute to the revenues of the Safety-Kleen Sustainability Solutions segment. These revenues are generated from sales of high-quality base and blended lubricating oils to third-party distributors, government agencies, fleets, railroads and industrial customers. The business also sells recycled fuel oil to asphalt plants, industrial plants and pulp and paper companies. The used oil is also processed into vacuum gas oil which can be further re-refined into lubricant base oils or sold directly into the marine diesel oil fuel market. Revenue for oil products is recognized at a point in time, upon the transfer of control. Control transfers when the products are delivered to the customer.

- Definition

Disclosure of accounting policy for revenue from contract with customer.

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+ Details

REVENUES (Tables)

9 Months Ended

Sep. 30, 2021

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue


	For the Three Months Ended September 30, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	632,755	$	185,096	$	59	$	817,910
Canada	111,076		22,493		—		133,569
Total third-party revenues	$	743,831	$	207,589	$	59	$	951,479

Sources of Revenue
Technical Services	$	308,158	$	—	$	—	$	308,158
Field and Emergency Response Services	116,677		—		—		116,677
Industrial Services and Other	154,977		—		59		155,036
Safety-Kleen Environmental Services	164,019		39,551		—		203,570
Safety-Kleen Oil	—		168,038		—		168,038
Total third-party revenues	$	743,831	$	207,589	$	59	$	951,479


	For the Three Months Ended September 30, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	554,050	$	112,785	$	(186)	$	666,649
Canada	97,639		14,798		258		112,695
Total third-party revenues	$	651,689	$	127,583	$	72	$	779,344

Sources of Revenue
Technical Services	$	257,612	$	—	$	—	$	257,612
Field and Emergency Response Services	115,989		—		—		115,989
Industrial Services and Other	124,582		—		72		124,654
Safety-Kleen Environmental Services	153,506		49,949		—		203,455
Safety-Kleen Oil	—		77,634		—		77,634
Total third-party revenues	$	651,689	$	127,583	$	72	$	779,344


	For the Nine Months Ended September 30, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	1,824,848	$	504,302	$	217	$	2,329,367
Canada	295,008		61,710		—		356,718
Total third-party revenues	$	2,119,856	$	566,012	$	217	$	2,686,085

Sources of Revenue
Technical Services	$	887,063	$	—	$	—	$	887,063
Field and Emergency Response Services	328,831		—		—		328,831
Industrial Services and Other	425,154		—		217		425,371
Safety-Kleen Environmental Services	478,808		118,982		—		597,790
Safety-Kleen Oil	—		447,030		—		447,030
Total third-party revenues	$	2,119,856	$	566,012	$	217	$	2,686,085


	For the Nine Months Ended September 30, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	1,704,945	$	340,226	$	(648)	$	2,044,523
Canada	264,500		38,018		866		303,384
Total third-party revenues	$	1,969,445	$	378,244	$	218	$	2,347,907

Sources of Revenue
Technical Services	$	774,814	$	—	$	—	$	774,814
Field and Emergency Response Services	349,254		—		—		349,254
Industrial Services and Other	366,573		—		218		366,791
Safety-Kleen Environmental Services	478,804		134,004		—		612,808
Safety-Kleen Oil	—		244,240		—		244,240
Total third-party revenues	$	1,969,445	$	378,244	$	218	$	2,347,907

Schedule of Contract Balances


(in thousands)	September 30, 2021		December 31, 2020
Receivables	$	703,199	$	611,534
Contract assets (unbilled receivables)	69,912		55,681
Contract liabilities (deferred revenue)	86,589		74,066

INVENTORIES AND SUPPLIES (Tables)

9 Months Ended

Sep. 30, 2021

Inventory Disclosure [Abstract]

Schedule of Inventories and Supplies

Inventories and supplies consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Oil and oil related products	$	88,044	$	76,209
Supplies	119,953		120,007
Solvent and solutions	7,620		8,812
Other	13,065		15,470
Total inventories and supplies	$	228,682	$	220,498

PROPERTY, PLANT AND EQUIPMENT (Tables)

9 Months Ended

Sep. 30, 2021

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

Property, plant and equipment consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Land	$	150,257	$	139,776
Asset retirement costs (non-landfill)	17,921		16,407
Landfill assets	200,545		191,687
Buildings and improvements (1)	524,397		509,804
Camp equipment	132,477		159,021
Vehicles (2)	864,808		844,026
Equipment (3)	1,821,327		1,807,235
Furniture and fixtures	6,838		7,082
Construction in progress	63,522		24,378
	3,782,092		3,699,416
Less - accumulated depreciation and amortization	2,273,736		2,174,118
Total property, plant and equipment, net	$	1,508,356	$	1,525,298

________________

(1) Balances inclusive of gross right-of-use ("ROU") assets classified as finance leases of $8.9 million in both periods.

(2) Balances inclusive of gross ROU assets classified as finance leases of $65.9 million and $47.2 million, respectively.

(3) Balances inclusive of gross ROU assets classified as finance leases of $9.3 million in both periods.

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes to Goodwill

The changes in goodwill by segment for the nine months ended September 30, 2021 were as follows (in thousands):


	Environmental Services		Safety-Kleen Sustainability Solutions		Totals
Balance at January 1, 2021	$	401,918	$	125,105	$	527,023
Increase from current period acquisition	—		15,860		15,860


Foreign currency translation	107		38		145
Balance at September 30, 2021	$	402,025	$	141,003	$	543,028

Schedule of Finite-Lived Intangible Assets

As of September 30, 2021 and December 31, 2020, the Company's intangible assets consisted of the following (in thousands):


	September 30, 2021						December 31, 2020
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	186,334	$	100,553	$	85,781	$	183,766	$	95,033	$	88,733
Customer and supplier relationships	361,438		207,497		153,941		382,083		211,895		170,188
Other intangible assets	20,388		16,795		3,593		39,287		34,744		4,543
Total amortizable permits and other intangible assets	568,160		324,845		243,315		605,136		341,672		263,464
Trademarks and trade names	123,182		—		123,182		123,156		—		123,156
Total permits and other intangible assets	$	691,342	$	324,845	$	366,497	$	728,292	$	341,672	$	386,620

Summary of Indefinite-Lived Intangible Assets

As of September 30, 2021 and December 31, 2020, the Company's intangible assets consisted of the following (in thousands):


	September 30, 2021						December 31, 2020
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	186,334	$	100,553	$	85,781	$	183,766	$	95,033	$	88,733
Customer and supplier relationships	361,438		207,497		153,941		382,083		211,895		170,188
Other intangible assets	20,388		16,795		3,593		39,287		34,744		4,543
Total amortizable permits and other intangible assets	568,160		324,845		243,315		605,136		341,672		263,464
Trademarks and trade names	123,182		—		123,182		123,156		—		123,156
Total permits and other intangible assets	$	691,342	$	324,845	$	366,497	$	728,292	$	341,672	$	386,620

Schedule of Expected Amortization for the Net Carrying Amount of Finite Lived Intangible Assets

The expected amortization of the net carrying amount of finite-lived intangible assets at September 30, 2021 was as follows (in thousands):


Years Ending December 31,	Expected Amortization
2021 (three months)	$	7,526
2022	30,002
2023	25,674
2024	24,180
2025	23,208
Thereafter	132,725
	$	243,315

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)

9 Months Ended

Sep. 30, 2021

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses and other current liabilities consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Accrued insurance	$	80,072	$	77,514
Accrued interest	9,281		19,697
Accrued compensation and benefits	94,256		81,437
Accrued income, real estate, sales and other taxes	29,629		25,843
Interest rate swap liability	23,496		33,630
Accrued other	62,693		57,702
	$	299,427	$	295,823

CLOSURE AND POST-CLOSURE LIABILITIES (Tables)

9 Months Ended

Sep. 30, 2021

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Closure and Post-Closure Liabilities

The changes to closure and post-closure liabilities (also referred to as “asset retirement obligations”) from January 1, 2021 through September 30, 2021 were as follows (in thousands):


	Landfill Retirement Liability		Non-Landfill Retirement Liability		Total
Balance at January 1, 2021	$	48,412	$	39,514	$	87,926
Liabilities assumed in acquisitions	—		451		451

New asset retirement obligations	1,979		—		1,979

Accretion	2,600		2,744		5,344
Changes in estimates recorded to consolidated statement of operations	35		291		326
Changes in estimates recorded to consolidated balance sheet	668		1,226		1,894
Expenditures	(4,420)		(461)		(4,881)
Currency translation and other	—		(11)		(11)
Balance at September 30, 2021	$	49,274	$	43,754	$	93,028

REMEDIAL LIABILITIES (Tables)

9 Months Ended

Sep. 30, 2021

Environmental Remediation Obligations [Abstract]

Schedule of Changes to Remedial Liabilities

The changes to remedial liabilities from January 1, 2021 through September 30, 2021 were as follows (in thousands):


	Remedial Liabilities for Landfill Sites		Remedial Liabilities for Inactive Sites		Remedial Liabilities (Including Superfund) for Non-Landfill Operations		Total
Balance at January 1, 2021	$	1,865	$	63,060	$	49,888	$	114,813


Accretion	67		1,955		1,259		3,281
Changes in estimates recorded to consolidated statement of operations	(22)		358		(321)		15
Expenditures	(37)		(3,963)		(3,342)		(7,342)
Currency translation and other	—		(821)		870		49
Balance at September 30, 2021	$	1,873	$	60,589	$	48,354	$	110,816

FINANCING ARRANGEMENTS (Tables)

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Schedule of the Entity's Financial Arrangements

The following table is a summary of the Company’s financing arrangements (in thousands):


Current Debt:	September 30, 2021		December 31, 2020
Secured senior term loans	$	7,535	$	7,535

Long-Term Debt:
Secured senior term loans due June 30, 2024 ("2024 Term Loans")	$	713,975	$	719,626
Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")	545,000		545,000
Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")	300,000		300,000
Long-term debt, at par	$	1,558,975	$	1,564,626
Unamortized debt issuance costs and premium, net	(12,691)		(14,985)
Long-term debt, at carrying value	$	1,546,284	$	1,549,641

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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+ Details

EARNINGS PER SHARE (Tables)

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

Schedule of Reconciliation of Basic and Diluted Earnings per Share Computations

The following are computations of basic and diluted earnings per share (in thousands, except per share amounts):


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
Numerator for basic and diluted earnings per share:
Net income	$	65,443	$	54,910	$	154,254	$	95,505

Denominator:
Basic shares outstanding	54,411		55,592		54,553		55,646
Dilutive effect of outstanding stock awards	296		146		309		186
Dilutive shares outstanding	54,707		55,738		54,862		55,832

Basic earnings per share:	$	1.20	$	0.99	$	2.83	$	1.72

Diluted earnings per share:	$	1.20	$	0.99	$	2.81	$	1.71

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)

9 Months Ended

Sep. 30, 2021

Equity [Abstract]

Schedule of Accumulated Other Comprehensive Loss

The changes in accumulated other comprehensive loss by component and related tax impacts for the nine months ended September 30, 2021 were as follows (in thousands):


	Foreign Currency Translation		Unrealized Gains (Losses) on Available-For-Sale Securities		Unrealized (Losses) Gains on Interest Rate Hedge		Unrealized Losses on Unfunded Pension Liability		Total
Balance at January 1, 2021	$	(176,234)	$	135	$	(33,629)	$	(1,749)	$	(211,477)
Other comprehensive income (loss) before reclassifications	767		(177)		2,660		—		3,250
Amounts reclassified out of accumulated other comprehensive loss	—		—		7,474		—		7,474
Tax benefit	—		37		—		—		37
Other comprehensive income (loss)	767		(140)		10,134		—		10,761
Balance at September 30, 2021	$	(175,467)	$	(5)	$	(23,495)	$	(1,749)	$	(200,716)

Schedule of Reclassification Out of Accumulated Other Comprehensive Income


Other Comprehensive Income (Loss) Component	For the Three Months Ended September 30, 2021		For the Nine Months Ended September 30, 2021		Location

Unrealized losses on interest rate hedge	$	(2,532)	$	(7,474)	Interest expense, net of interest income

STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Restricted Stock Awards

The following table summarizes information about restricted stock awards for the nine months ended September 30, 2021:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2021	493,879	$	59.74
Granted	174,225	93.95
Vested	(181,651)	57.68
Forfeited	(39,091)	61.75
Balance at September 30, 2021	447,362	73.72

Schedule of Performance Stock Awards

The following table summarizes information about performance stock awards for the nine months ended September 30, 2021:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2021	254,449	$	61.75
Granted	134,931	92.92
Vested	(71,815)	62.27
Forfeited	(26,191)	64.47
Balance at September 30, 2021	291,374	75.81

SEGMENT REPORTING (Tables)

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

Reconciliation of Third Party Revenues to Direct Revenues

The following table reconciles third-party revenues to direct revenues for the three and nine months ended September 30, 2021 and September 30, 2020 (in thousands):


	For the Three Months Ended September 30, 2021				For the Three Months Ended September 30, 2020
	Third-party revenues		Intersegment revenues, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Direct revenues
Environmental Services	$	743,831	$	1,802	$	745,633	$	651,689	$	(1,129)	$	650,560
Safety-Kleen Sustainability Solutions	207,589		(1,802)		205,787		127,583		1,129		128,712
Corporate Items	59		—		59		72		—		72
Total	$	951,479	$	—	$	951,479	$	779,344	$	—	$	779,344


	For the Nine Months Ended September 30, 2021				For the Nine Months Ended September 30, 2020
	Third-party revenues		Intersegment revenues, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Direct revenues
Environmental Services	$	2,119,856	$	4,476	$	2,124,332	$	1,969,445	$	(1,099)	$	1,968,346
Safety-Kleen Sustainability Solutions	566,012		(4,476)		561,536		378,244		1,099		379,343
Corporate Items	217		—		217		218		—		218
Total	$	2,686,085	$	—	$	2,686,085	$	2,347,907	$	—	$	2,347,907

Reconciliation to Consolidated Statements of Income to Adjusted EBITDA

The following table presents Adjusted EBITDA information used by management by reported segment (in thousands):


	For the Three Months Ended				For the Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
Adjusted EBITDA:
Environmental Services	$	166,471	$	180,002	$	482,766	$	502,101
Safety-Kleen Sustainability Solutions	70,810		29,613		165,756		62,248
Corporate Items	(52,197)		(41,782)		(146,216)		(132,369)
Total	185,084		167,833		502,306		431,980
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,799		2,822		8,625		8,149
Stock-based compensation	6,001		6,662		12,786		12,739
Depreciation and amortization	71,451		74,470		215,206		221,497
Income from operations	104,833		83,879		265,689		189,595
Other (income) expense, net	(199)		(2,268)		2,509		597
Loss on sale of businesses	—		118		—		3,376

Interest expense, net of interest income	17,984		17,407		53,953		54,848
Income before provision for income taxes	$	87,048	$	68,622	$	209,227	$	130,774

Schedule of Certain Assets by Reportable Segment

The following table presents certain assets by reportable segment and in the aggregate (in thousands):


	September 30, 2021		December 31, 2020
Property, plant and equipment, net:
Environmental Services	$	1,050,901	$	1,068,910
Safety-Kleen Sustainability Solutions	363,857		366,160
Corporate Items	93,598		90,228
Total property, plant and equipment, net	$	1,508,356	$	1,525,298

Goodwill and Permits and other intangibles, net:
Environmental Services
Goodwill	$	402,025	$	401,918
Permits and other intangibles, net	217,188		228,237
Total Environmental Services	619,213		630,155

Safety-Kleen Sustainability Solutions
Goodwill	$	141,003	$	125,105
Permits and other intangibles, net	149,309		158,383
Total Safety-Kleen Sustainability Solutions	290,312		283,488

Total	$	909,525	$	913,643

Long-lived Assets by Geographic Areas

The following table presents the total assets by geographical area (in thousands):


	September 30, 2021		December 31, 2020
United States	$	3,629,056	$	3,447,811
Canada and other foreign	725,243		683,709
Total	$	4,354,299	$	4,131,520

REVENUES - Additional Information (Details)	9 Months Ended
REVENUES - Additional Information (Details)	Sep. 30, 2021 source
Disaggregation of Revenue [Line Items]
Deferred contract cost, recognition period	3 months
Environmental Services
Disaggregation of Revenue [Line Items]
Number of revenue sources	4
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Number of revenue sources	2

REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 951,479	$ 779,344	$ 2,686,085	$ 2,347,907
Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	308,158	257,612	887,063	774,814
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	116,677	115,989	328,831	349,254
Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	155,036	124,654	425,371	366,791
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	203,570	203,455	597,790	612,808
Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	168,038	77,634	447,030	244,240
United States
Disaggregation of Revenue [Line Items]
Total revenues	817,910	666,649	2,329,367	2,044,523
Canada
Disaggregation of Revenue [Line Items]
Total revenues	133,569	112,695	356,718	303,384
Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	745,633	650,560	2,124,332	1,968,346
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	205,787	128,712	561,536	379,343
Operating segments \| Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	743,831	651,689	2,119,856	1,969,445
Operating segments \| Environmental Services \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	308,158	257,612	887,063	774,814
Operating segments \| Environmental Services \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	116,677	115,989	328,831	349,254
Operating segments \| Environmental Services \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	154,977	124,582	425,154	366,573
Operating segments \| Environmental Services \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	164,019	153,506	478,808	478,804
Operating segments \| Environmental Services \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Environmental Services \| United States
Disaggregation of Revenue [Line Items]
Total revenues	632,755	554,050	1,824,848	1,704,945
Operating segments \| Environmental Services \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	111,076	97,639	295,008	264,500
Operating segments \| Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	207,589	127,583	566,012	378,244
Operating segments \| Safety-Kleen Sustainability Solutions \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Safety-Kleen Sustainability Solutions \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Safety-Kleen Sustainability Solutions \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Safety-Kleen Sustainability Solutions \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	39,551	49,949	118,982	134,004
Operating segments \| Safety-Kleen Sustainability Solutions \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	168,038	77,634	447,030	244,240
Operating segments \| Safety-Kleen Sustainability Solutions \| United States
Disaggregation of Revenue [Line Items]
Total revenues	185,096	112,785	504,302	340,226
Operating segments \| Safety-Kleen Sustainability Solutions \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	22,493	14,798	61,710	38,018
Corporate, non-Segment
Disaggregation of Revenue [Line Items]
Total revenues	59	72	217	218
Corporate, non-Segment \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate, non-Segment \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate, non-Segment \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	59	72	217	218
Corporate, non-Segment \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate, non-Segment \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate, non-Segment \| United States
Disaggregation of Revenue [Line Items]
Total revenues	59	(186)	217	(648)
Corporate, non-Segment \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 258	$ 0	$ 866

REVENUES - Contract Balances (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Receivables	$ 703,199	$ 611,534
Contract assets (unbilled receivables)	69,912	55,681
Contract liabilities (deferred revenue)	$ 86,589	$ 74,066

BUSINESS COMBINATIONS (Details)					9 Months Ended
BUSINESS COMBINATIONS (Details)	Oct. 08, 2021 USD ($) employee proceeding	Jun. 29, 2021 USD ($)	Mar. 27, 2021 USD ($)	Apr. 17, 2020 USD ($)	Sep. 30, 2021 USD ($)
Business Acquisition [Line Items]
Goodwill recognized					$ 15,860,000
Vertex Energy Inc
Business Acquisition [Line Items]
Consideration to acquire assets		$ 140,000,000
March 27, 2021 Acquisition
Business Acquisition [Line Items]
Purchase price to acquire business			$ 22,800,000
Goodwill recognized			$ 15,900,000
HydroChemPSC \| Subsequent Event
Business Acquisition [Line Items]
Purchase price to acquire business	$ 1,240,000,000
Annual revenues reported by acquired entity in 2020	$ 715,300,000
HydroChemPSC \| Subsequent Event \| Minimum
Business Acquisition [Line Items]
Goodwill, acquired as percentage of purchase price	40.00%
HydroChemPSC \| Subsequent Event \| Maximum
Business Acquisition [Line Items]
Goodwill, acquired as percentage of purchase price	50.00%
HydroChemPSC \| Subsequent Event \| HydroChemPSC
Business Acquisition [Line Items]
Entity number of employees \| employee	4,500
Number of service locations (more than) \| proceeding	240
HydroChemPSC \| Subsequent Event \| 2028 Term Loans \| Secured debt
Business Acquisition [Line Items]
Debt Instrument, face amount	$ 1,000,000,000
Net proceeds from the company’s issuance	$ 983,000,000
2020 Acquisition
Business Acquisition [Line Items]
Purchase price to acquire business				$ 8,800,000
Goodwill recognized				$ 1,400,000

INVENTORIES AND SUPPLIES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Inventory [Line Items]
Inventories and supplies	$ 228,682	$ 220,498
Oil and oil related products
Inventory [Line Items]
Inventories and supplies	88,044	76,209
Supplies
Inventory [Line Items]
Inventories and supplies	119,953	120,007
Solvent and solutions
Inventory [Line Items]
Inventories and supplies	7,620	8,812
Other
Inventory [Line Items]
Inventories and supplies	$ 13,065	$ 15,470

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 3,782,092	$ 3,699,416
Less - accumulated depreciation and amortization	2,273,736	2,174,118
Total property, plant and equipment, net	1,508,356	1,525,298
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	150,257	139,776
Asset retirement costs (non-landfill)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	17,921	16,407
Landfill assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	200,545	191,687
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	524,397	509,804
Right-of-Use assets, finance leases	8,900	8,900
Camp equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	132,477	159,021
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	864,808	844,026
Right-of-Use assets, finance leases	65,900	47,200
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,821,327	1,807,235
Right-of-Use assets, finance leases	9,300	9,300
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,838	7,082
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 63,522	$ 24,378

PROPERTY, PLANT AND EQUIPMENT - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Depreciation expense, inclusive of landfill and finance lease amortization	$ 63.9	$ 64.9	$ 192.3	$ 193.9

GOODWILL AND OTHER INTANGIBLE ASSETS - Changes to Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2021	$ 527,023
Increase from current period acquisition	15,860
Foreign currency translation	145
Balance at September 30, 2021	543,028
Environmental Services
Goodwill [Roll Forward]
Balance at January 1, 2021	401,918
Increase from current period acquisition	0
Foreign currency translation	107
Balance at September 30, 2021	402,025
Safety-Kleen Sustainability Solutions
Goodwill [Roll Forward]
Balance at January 1, 2021	125,105
Increase from current period acquisition	15,860
Foreign currency translation	38
Balance at September 30, 2021	$ 141,003

GOODWILL AND OTHER INTANGIBLE ASSETS - Finite-lived and Indefinite Lived Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	$ 568,160	$ 605,136
Accumulated Amortization	324,845	341,672
Finite-lived intangible assets, net	243,315	263,464
Total permits and other intangible assets, Cost	691,342	728,292
Total permits and other intangible assets, Net	366,497	386,620
Trademarks and trade names
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Trademarks and trade names	123,182	123,156
Permits
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	186,334	183,766
Accumulated Amortization	100,553	95,033
Finite-lived intangible assets, net	85,781	88,733
Customer and supplier relationships
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	361,438	382,083
Accumulated Amortization	207,497	211,895
Finite-lived intangible assets, net	153,941	170,188
Other intangible assets
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	20,388	39,287
Accumulated Amortization	16,795	34,744
Finite-lived intangible assets, net	$ 3,593	$ 4,543

GOODWILL AND OTHER INTANGIBLE ASSETS - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) reportingUnit	Sep. 30, 2020 USD ($)
Goodwill [Line Items]
Number of reporting units \| reportingUnit			3
Goodwill impairment \| $			$ 0
Amortization of permits and other intangible assets \| $	$ 7,600,000	$ 9,600,000	22,900,000	$ 27,600,000
Intangible assets, written-off \| $			$ 39,700,000
Environmental Services
Goodwill [Line Items]
Number of reporting units \| reportingUnit			2
Safety-Kleen Sustainability Solutions
Goodwill [Line Items]
Number of reporting units \| reportingUnit			1

GOODWILL AND OTHER INTANGIBLE ASSETS - Expected Future Amortization (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
2021 (three months)	$ 7,526
2022	30,002
2023	25,674
2024	24,180
2025	23,208
Thereafter	132,725
Finite-lived intangible assets, net	$ 243,315	$ 263,464

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued insurance	$ 80,072	$ 77,514
Accrued interest	9,281	19,697
Accrued compensation and benefits	94,256	81,437
Accrued income, real estate, sales and other taxes	29,629	25,843
Interest rate swap liability	23,496	33,630
Accrued other	62,693	57,702
Total accrued expenses	$ 299,427	$ 295,823

CLOSURE AND POST-CLOSURE LIABILITIES - Changes in Post-Closure Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Changes to post-closure liabilities
Balance at January 1, 2021	$ 87,926
Liabilities assumed in acquisitions	451
New asset retirement obligations	1,979
Accretion	5,344
Changes in estimates recorded to consolidated statement of operations	326
Changes in estimates recorded to consolidated balance sheet	1,894
Expenditures	(4,881)
Currency translation and other	(11)
Balance at September 30, 2021	93,028
Landfill Retirement Liability
Changes to post-closure liabilities
Balance at January 1, 2021	48,412
Liabilities assumed in acquisitions	0
New asset retirement obligations	1,979
Accretion	2,600
Changes in estimates recorded to consolidated statement of operations	35
Changes in estimates recorded to consolidated balance sheet	668
Expenditures	(4,420)
Currency translation and other	0
Balance at September 30, 2021	49,274
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Balance at January 1, 2021	39,514
Liabilities assumed in acquisitions	451
New asset retirement obligations	0
Accretion	2,744
Changes in estimates recorded to consolidated statement of operations	291
Changes in estimates recorded to consolidated balance sheet	1,226
Expenditures	(461)
Currency translation and other	(11)
Balance at September 30, 2021	$ 43,754

CLOSURE AND POST-CLOSURE LIABILITIES - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Credit-adjusted risk-free rate	4.84%

REMEDIAL LIABILITIES (Details) $ in Thousands	9 Months Ended
REMEDIAL LIABILITIES (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2021	$ 114,813
Accretion	3,281
Changes in estimates recorded to consolidated statement of operations	15
Expenditures	(7,342)
Currency translation and other	49
Balance at September 30, 2021	110,816
Remedial Liabilities for Landfill Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2021	1,865
Accretion	67
Changes in estimates recorded to consolidated statement of operations	(22)
Expenditures	(37)
Currency translation and other	0
Balance at September 30, 2021	1,873
Remedial Liabilities for Inactive Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2021	63,060
Accretion	1,955
Changes in estimates recorded to consolidated statement of operations	358
Expenditures	(3,963)
Currency translation and other	(821)
Balance at September 30, 2021	60,589
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2021	49,888
Accretion	1,259
Changes in estimates recorded to consolidated statement of operations	(321)
Expenditures	(3,342)
Currency translation and other	870
Balance at September 30, 2021	$ 48,354

FINANCING ARRANGEMENTS - Summary of Financing Arrangements (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Current portion of long-term debt	$ 7,535	$ 7,535
Long-term debt, at par	1,558,975	1,564,626
Unamortized debt issuance costs and premium, net	(12,691)	(14,985)
Long-term debt, at carrying value	1,546,284	1,549,641
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans")
Debt Instrument [Line Items]
Current portion of long-term debt	7,535	7,535
Long-term debt, at par	713,975	719,626
Unsecured debt \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument [Line Items]
Long-term debt, at par	$ 545,000	$ 545,000
Interest rate (as a percentage)	4.875%	4.875%
Unsecured debt \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument [Line Items]
Long-term debt, at par	$ 300,000	$ 300,000
Interest rate (as a percentage)	5.125%	5.125%

FINANCING ARRANGEMENTS - Additional Information (Details) - USD ($)	Oct. 08, 2021	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt fair value		$ 1,600,000,000	$ 1,600,000,000
Interest rate swap, liability		23,500,000	33,600,000
Interest Rate Swap
Debt Instrument [Line Items]
Notional amount of interest rate swap agreements		350,000,000
Secured debt \| 2028 Term Loans \| Subsequent Event
Debt Instrument [Line Items]
Debt prepayment premium rate, percentage	1.00%
Secured debt \| 2028 Term Loans \| Subsequent Event \| HydroChemPSC
Debt Instrument [Line Items]
Debt Instrument, face amount	$ 1,000,000,000
Net proceeds from the company’s issuance	$ 983,000,000
Secured debt \| 2028 Term Loans \| Eurodollar \| Subsequent Event
Debt Instrument [Line Items]
Debt, basis spread on variable rate	2.00%
Debt, floor interest rate	0.00%
Secured debt \| 2028 Term Loans \| Base Rate \| Subsequent Event
Debt Instrument [Line Items]
Debt, basis spread on variable rate	1.00%
Debt, floor interest rate	1.00%
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans")
Debt Instrument [Line Items]
Debt outstanding		721,500,000
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans") \| Interest Rate Swap
Debt Instrument [Line Items]
Debt outstanding		$ 350,000,000
Effective interest rate percentage		4.67%
Debt, Weighted Average Interest Rate		2.92%
Revolving Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity		$ 400,000,000
Line of credit outstanding balances		0	$ 0
Available to borrow and outstanding letters of credit		288,500,000
Outstanding letters of credit		$ 111,500,000

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
INCOME TAXES (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective income tax rate	24.80%	20.00%	26.30%	27.00%
Unrecognized tax benefits	$ 5.4		$ 5.4		$ 5.5
Interest on unrecognized tax benefits	$ 2.2		$ 2.2		$ 2.1

EARNINGS PER SHARE - Reconciliation of Basic and Diluted Earnings Per Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator for basic and diluted earnings per share:
Net income	$ 65,443	$ 67,075	$ 21,736	$ 54,910	$ 29,023	$ 11,572	$ 154,254	$ 95,505
Denominator:
Basic shares outstanding (in shares)	54,411			55,592			54,553	55,646
Dilutive effect of outstanding stock awards (in shares)	296			146			309	186
Dilutive shares outstanding (in shares)	54,707			55,738			54,862	55,832
Basic earnings per share (in dollars per share)	$ 1.20			$ 0.99			$ 2.83	$ 1.72
Diluted earnings per share (in dollars per share)	$ 1.20			$ 0.99			$ 2.81	$ 1.71

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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-URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

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-Paragraph 1
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-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

EARNINGS PER SHARE - Anti-Dilutive Securities (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of performance stock awards that performance criteria not attained (in shares)	67,019	235,806	67,019	235,806
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earning per share (in shares)	38,250	16,183	39,750	14,516

ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	$ 1,409,587	$ 1,348,450	$ 1,341,551	$ 1,253,971	$ 1,205,805	$ 1,269,813	$ 1,341,551	$ 1,269,813
Other comprehensive income (loss) before reclassifications							3,250
Amounts reclassified out of accumulated other comprehensive loss							7,474
Tax benefit							37
Other comprehensive (loss) income, net of tax	(11,827)	10,640	11,948	12,385	17,528	(59,306)	10,761	(29,393)
Balance ending of period	1,463,560	1,409,587	1,348,450	1,304,715	1,253,971	1,205,805	1,463,560	1,304,715
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			(176,234)				(176,234)
Other comprehensive income (loss) before reclassifications							767
Amounts reclassified out of accumulated other comprehensive loss							0
Tax benefit							0
Other comprehensive (loss) income, net of tax							767
Balance ending of period	(175,467)						(175,467)
Unrealized Gains (Losses) on Available-For-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			135				135
Other comprehensive income (loss) before reclassifications							(177)
Amounts reclassified out of accumulated other comprehensive loss							0
Tax benefit							37
Other comprehensive (loss) income, net of tax							(140)
Balance ending of period	(5)						(5)
Unrealized (Losses) Gains on Interest Rate Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			(33,629)				(33,629)
Other comprehensive income (loss) before reclassifications							2,660
Amounts reclassified out of accumulated other comprehensive loss							7,474
Tax benefit							0
Other comprehensive (loss) income, net of tax							10,134
Balance ending of period	(23,495)						(23,495)
Unrealized Losses on Unfunded Pension Liability
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			(1,749)				(1,749)
Other comprehensive income (loss) before reclassifications							0
Amounts reclassified out of accumulated other comprehensive loss							0
Tax benefit							0
Other comprehensive (loss) income, net of tax							0
Balance ending of period	(1,749)						(1,749)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	(188,889)	(199,529)	(211,477)	(251,829)	(269,357)	(210,051)	(211,477)	(210,051)
Other comprehensive (loss) income, net of tax	(11,827)	10,640	11,948	12,385	17,528	(59,306)
Balance ending of period	$ (200,716)	$ (188,889)	$ (199,529)	$ (239,444)	$ (251,829)	$ (269,357)	$ (200,716)	$ (239,444)

ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassified Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Unrealized losses on interest rate hedge
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net of interest income	$ (2,532)	$ (7,474)

STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock-based compensation	$ 6.0	$ 6.7	$ 12.8	$ 12.7
Income tax benefit	$ 1.3	$ 1.7	$ 2.8	$ 2.9

STOCK-BASED COMPENSATION - Restricted Stock Awards (Details) - Restricted stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Number of Shares
Beginning balance (in shares)			493,879
Granted (in shares)			174,225
Vested (in shares)			(181,651)
Forfeited (in shares)			(39,091)
Ending balance (in shares)	447,362		447,362
Weighted Average Grant-Date Fair Value
Beginning of period (in dollars per share)			$ 59.74
Granted (in dollars per share)			93.95
Vested (in dollars per share)			57.68
Forfeited (in dollars per share)			61.75
End of period (in dollars per share)	$ 73.72		$ 73.72
Unrecognized compensation cost	$ 26.3		$ 26.3
Period for recognition (in years)			3 years
Fair value of share-based payment awards	$ 7.4	$ 3.1	$ 16.3	$ 12.8

STOCK-BASED COMPENSATION - Performance Stock Awards (Details) - Performance stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Number of Shares
Beginning balance (in shares)			254,449
Granted (in shares)			134,931
Vested (in shares)	0	0	(71,815)
Forfeited (in shares)			(26,191)
Ending balance (in shares)	291,374		291,374
Weighted Average Grant-Date Fair Value
Beginning of period (in dollars per share)			$ 61.75
Granted (in dollars per share)			92.92
Vested (in dollars per share)			62.27
Forfeited (in dollars per share)			64.47
End of period (in dollars per share)	$ 75.81		$ 75.81
Unrecognized compensation cost	$ 10.0		$ 10.0
Fair value of share-based payment awards			$ 6.4	$ 1.3

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	9 Months Ended	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Sep. 30, 2021 USD ($) proceeding claim site	Dec. 31, 2012 CAD ($)	Dec. 31, 1999 municipality	Dec. 31, 1968 permit	Dec. 31, 2020 USD ($) proceeding
Loss Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 30,400,000				$ 29,800,000
Number of proceedings as defendant \| proceeding	69
Number of product liability claims settled or dismissed \| claim	12
Legal and Administrative Proceedings
Loss Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 23,200,000				24,000,000
Ville Mercier
Loss Contingencies [Line Items]
Number of permits issued by government, for dumping organic liquid \| permit				2
Number of neighboring municipalities filing separate legal proceedings against the Mercier Subsidiary and the Government of Quebec \| municipality			3
General damages sought \| $		$ 2.9
Punitive damages sought \| $		$ 10.0
Superfund Proceedings
Loss Contingencies [Line Items]
Number of sites owned by third party excluded from cleanup or related liabilities	131
Number of sites owned by the entity subject to proceedings under federal or state superfund laws	6
Number of sites owned by third parties	125
Number of sites for which environmental remediation expense is settled	30
Third party sites requiring expenditure on remediation	15
Number of sites not currently requiring expenditures on remediation	80
Minimum potential liability \| $	$ 1,000,000
Number of sites, potential liability exceeds substantial quota	3
Notices received from owners of third parties sites seeking indemnifications from the company	18
BR Facility \| Remedial Liabilities for Inactive Sites
Loss Contingencies [Line Items]
Increase of remedial liabilities \| $	$ 3,300,000
ChemWaste
Loss Contingencies [Line Items]
Indemnification agreement with third party sites	18
Federal and State Enforcement Actions
Loss Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 7,200,000				$ 5,800,000
Number of proceedings as defendant \| proceeding	1				0
Minimum potential liability \| $	$ 1,000,000				$ 1,000,000

SEGMENT REPORTING - Reconciliation of Third Party Revenues to Direct Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 951,479	$ 779,344	$ 2,686,085	$ 2,347,907
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	745,633	650,560	2,124,332	1,968,346
Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	205,787	128,712	561,536	379,343
Operating Segments \| Environmental Services
Segment Reporting Information [Line Items]
Total revenues	743,831	651,689	2,119,856	1,969,445
Operating Segments \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	207,589	127,583	566,012	378,244
Intersegment revenues, net \| Environmental Services
Segment Reporting Information [Line Items]
Total revenues	1,802	(1,129)	4,476	(1,099)
Intersegment revenues, net \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	(1,802)	1,129	(4,476)	1,099
Corporate, non-Segment
Segment Reporting Information [Line Items]
Total revenues	59	72	217	218
Operating and Corporate non-segment
Segment Reporting Information [Line Items]
Total revenues	$ 59	$ 72	$ 217	$ 218

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

SEGMENT REPORTING - Reconciliation to Consolidated Statements of Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 185,084	$ 167,833	$ 502,306	$ 431,980
Reconciliation of Net Income to Adjusted EBITDA [Abstract]
Accretion of environmental liabilities	2,799	2,822	8,625	8,149
Stock-based compensation	6,001	6,662	12,786	12,739
Depreciation and amortization	71,451	74,470	215,206	221,497
Income from operations	104,833	83,879	265,689	189,595
Other (income) expense, net	(199)	(2,268)	2,509	597
Loss on sale of businesses	0	118	0	3,376
Interest expense, net of interest income	17,984	17,407	53,953	54,848
Income before provision for income taxes	87,048	68,622	209,227	130,774
Operating segments \| Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	166,471	180,002	482,766	502,101
Operating segments \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Adjusted EBITDA	70,810	29,613	165,756	62,248
Corporate, non-Segment
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (52,197)	$ (41,782)	$ (146,216)	$ (132,369)

SEGMENT REPORTING - Schedule of Certain Assets by Reportable Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,508,356	$ 1,525,298
Goodwill	543,028	527,023
Permits and other intangibles, net	366,497	386,620
Goodwill and Permits and other intangibles, net	909,525	913,643
Environmental Services
Segment Reporting Information [Line Items]
Goodwill	402,025	401,918
Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Goodwill	141,003	125,105
Operating Segments \| Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	1,050,901	1,068,910
Goodwill	402,025	401,918
Permits and other intangibles, net	217,188	228,237
Goodwill and Permits and other intangibles, net	619,213	630,155
Operating Segments \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Property, plant and equipment, net	363,857	366,160
Goodwill	141,003	125,105
Permits and other intangibles, net	149,309	158,383
Goodwill and Permits and other intangibles, net	290,312	283,488
Corporate, non-Segment
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 93,598	$ 90,228

SEGMENT REPORTING - Long-lived Assets by Geographic Areas (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 4,354,299	$ 4,131,520
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	3,629,056	3,447,811
Canada and other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 725,243	$ 683,709

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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+ Details