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Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
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		55,638,158
Entity Central Index Key	0000822818
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 447,366	$ 371,991
Short-term marketable securities	59,326	42,421
Accounts receivable, net of allowances aggregating $44,632 and $38,711, respectively	572,373	644,738
Unbilled accounts receivable	44,761	56,326
Deferred costs	18,715	21,746
Inventories and supplies	219,808	214,744
Prepaid expenses and other current assets	69,455	48,942
Total current assets	1,431,804	1,400,908
Property, plant and equipment, net	1,553,808	1,588,151
Other assets:
Operating lease right-of-use assets	153,522	162,206
Goodwill	523,154	525,013
Permits and other intangibles, net	400,448	419,066
Other	14,893	13,560
Total other assets	1,092,017	1,119,845
Total assets	4,077,629	4,108,904
Current liabilities:
Current portion of long-term obligations	7,535	7,535
Accounts payable	188,340	298,375
Deferred revenue	61,902	73,370
Accrued expenses	289,414	276,540
Current portion of closure, post-closure and remedial liabilities	19,129	23,301
Current portion of operating lease liabilities	38,620	40,979
Total current liabilities	604,940	720,100
Other liabilities:
Closure and post-closure liabilities, less current portion of $5,708 and $7,283, respectively	76,933	68,368
Remedial liabilities, less current portion of $13,421 and $16,018, respectively	99,062	98,155
Long-term obligations, less current portion	1,626,871	1,554,116
Operating lease liabilities, less current portion	115,089	121,020
Deferred taxes, unrecognized tax benefits and other long-term liabilities	300,763	277,332
Total other liabilities	2,218,718	2,118,991
Commitments and contingent liabilities (See Note 16)
Stockholders’ equity:
Common stock, $0.01 par value: authorized 80,000,000 shares; issued and outstanding 55,612,860 and 55,797,734 shares, respectively	556	558
Additional paid-in capital	629,755	644,412
Accumulated other comprehensive loss	(251,829)	(210,051)
Accumulated earnings	875,489	834,894
Total stockholders’ equity	1,253,971	1,269,813
Total liabilities and stockholders’ equity	$ 4,077,629	$ 4,108,904
Common stock, par value (in USD per share)	$ 0.01	$ 0.01

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 44,632	$ 38,711
Closure and post-closure liabilities, current portion	5,708	7,283
Remedial liabilities, current portion	$ 13,421	$ 16,018
Common stock, par 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)	55,612,860	55,797,734
Common stock, outstanding shares (in shares)	55,612,860	55,797,734

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Total revenues	$ 710,000	$ 868,678	$ 1,568,563	$ 1,649,517
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	470,681	594,933	1,077,347	1,159,297
Selling, general and administrative expenses	103,839	123,920	233,146	238,732
Accretion of environmental liabilities	2,766	2,560	5,327	5,134
Depreciation and amortization	72,494	74,217	147,027	149,572
Income from operations	60,220	73,048	105,716	96,782
Other (expense) income, net	(500)	(564)	(2,865)	2,419
Loss on sale of businesses	(184)	0	(3,258)	0
Interest expense, net of interest income of $668, $903, $1,666 and $1,829, respectively	(18,654)	(20,215)	(37,441)	(39,979)
Income before provision for income taxes	40,882	52,269	62,152	59,222
Provision for income taxes	11,859	16,025	21,557	22,002
Net income	$ 29,023	$ 36,244	$ 40,595	$ 37,220
Earnings Per Share [Abstract]
Basic (in USD per share)	$ 0.52	$ 0.65	$ 0.73	$ 0.67
Diluted (in USD per share)	$ 0.52	$ 0.65	$ 0.73	$ 0.66
Shares used to compute earnings per share - Basic (in shares)	55,590	55,875	55,673	55,861
Shares used to compute earnings per share - Diluted (in shares)	55,748	56,066	55,882	56,001
Service revenues
Revenues:
Total revenues	$ 637,839	$ 715,085	$ 1,357,706	$ 1,371,743
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	411,065	480,229	903,781	943,712
Product revenues
Revenues:
Total revenues	72,161	153,593	210,857	277,774
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 59,616	$ 114,704	$ 173,566	$ 215,585

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Interest income	$ 668	$ 903	$ 1,666	$ 1,829

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 29,023	$ 36,244	$ 40,595	$ 37,220
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available-for-sale securities	296	(236)	232	(93)
Reclassification adjustment for losses on available-for-sale securities included in net income	0	332	0	332
Unrealized loss on interest rate hedge	(3,000)	(9,014)	(21,382)	(14,031)
Reclassification adjustment for losses on interest rate hedge included in net income	2,130	397	3,228	755
Foreign currency translation adjustments	18,102	13,597	(23,856)	22,137
Other comprehensive income (loss), net of tax	17,528	5,076	(41,778)	9,100
Comprehensive income (loss)	$ 46,551	$ 41,320	$ (1,183)	$ 46,320

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 40,595	$ 37,220
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	147,027	149,572
Allowance for doubtful accounts	9,006	(2,233)
Amortization of deferred financing costs and debt discount	1,787	2,000
Accretion of environmental liabilities	5,327	5,134
Changes in environmental liability estimates	5,607	(748)
Deferred income taxes	0	(1,636)
Other expense (income), net	2,865	(2,419)
Stock-based compensation	6,077	9,643
Loss on sale of businesses	3,258	0
Environmental expenditures	(6,104)	(6,134)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	67,540	(13,284)
Inventories and supplies	(9,024)	(4,129)
Other current and non-current assets	(25,840)	(10,706)
Accounts payable	(82,134)	(20,915)
Other current and long-term liabilities	7,499	(2,895)
Net cash from operating activities	173,486	138,470
Cash flows used in investing activities:
Additions to property, plant and equipment	(125,721)	(118,372)
Proceeds from sale and disposal of fixed assets	3,101	7,389
Acquisitions, net of cash acquired	(8,877)	(29,479)
Proceeds from sale of businesses, net of transactional costs	7,753	0
Additions to intangible assets including costs to obtain or renew permits	(1,242)	(1,923)
Proceeds from sale of available-for-sale securities	28,851	26,518
Purchases of available-for-sale securities	(45,550)	(24,001)
Net cash used in investing activities	(141,685)	(139,868)
Cash flows from (used in) financing activities:
Change in uncashed checks	(1,689)	(3,514)
Tax payments related to withholdings on vested restricted stock	(3,395)	(4,980)
Repurchases of common stock	(17,341)	(11,272)
Payments on finance leases	(1,790)	(259)
Principal payments on debt	(3,768)	(3,768)
Borrowing from revolving credit facility	150,000	0
Payment on revolving credit facility	(75,000)	0
Net cash from (used in) financing activities	47,017	(23,793)
Effect of exchange rate change on cash	(3,443)	3,139
Increase (decrease) in cash and cash equivalents	75,375	(22,052)
Cash and cash equivalents, beginning of period	371,991	226,507
Cash and cash equivalents, end of period	447,366	204,455
Cash payments for interest and income taxes:
Interest paid	38,327	39,369
Income taxes paid	1,478	12,697
Non-cash investing activities:
Property, plant and equipment accrued	7,421	14,103
ROU assets obtained in exchange for operating lease liabilities	16,216	5,575
ROU assets obtained in exchange for finance lease liabilities	$ 16,452	$ 23,027

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, 2018		55,847
Balance beginning of period at Dec. 31, 2018	$ 1,169,756	$ 558	$ 655,415	$ (223,371)	$ 737,154
Increase (Decrease) in Stockholders' Equity
Net income	976				976
Other comprehensive (loss) income	4,024			4,024
Stock-based compensation	5,809		5,809
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	(2,276)	$ 1	(2,277)
Repurchases of common stock (in shares)		(97)
Repurchases of common stock	(6,324)	$ (1)	(6,323)
Balance ending of period (in shares) at Mar. 31, 2019		55,828
Balance ending of period at Mar. 31, 2019	1,171,965	$ 558	652,624	(219,347)	738,130
Balance beginning of period (in shares) at Dec. 31, 2018		55,847
Balance beginning of period at Dec. 31, 2018	1,169,756	$ 558	655,415	(223,371)	737,154
Increase (Decrease) in Stockholders' Equity
Net income	37,220
Other comprehensive (loss) income	9,100
Balance ending of period (in shares) at Jun. 30, 2019		55,859
Balance ending of period at Jun. 30, 2019	1,209,467	$ 559	648,805	(214,271)	774,374
Balance beginning of period (in shares) at Mar. 31, 2019		55,828
Balance beginning of period at Mar. 31, 2019	1,171,965	$ 558	652,624	(219,347)	738,130
Increase (Decrease) in Stockholders' Equity
Net income	36,244				36,244
Other comprehensive (loss) income	5,076			5,076
Stock-based compensation	3,834		3,834
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		105
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(2,704)	$ 1	(2,705)
Repurchases of common stock (in shares)		(74)
Repurchases of common stock	(4,948)	$ 0	(4,948)
Balance ending of period (in shares) at Jun. 30, 2019		55,859
Balance ending of period at Jun. 30, 2019	$ 1,209,467	$ 559	648,805	(214,271)	774,374
Increase (Decrease) in Stockholders' Equity
Common stock, par value (in USD per share)	$ 0.01
Common stock, par value (in USD per share)	$ 0.01
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	40,595
Other comprehensive (loss) income	(41,778)
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
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)	$ 0	(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
Common stock, par value (in USD per share)	$ 0.01

BASIS OF PRESENTATION	6 Months Ended
BASIS OF PRESENTATION	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION The 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, 2019. A novel strain of coronavirus ("COVID-19") was first identified in December 2019, and subsequently declared a global pandemic by the World Health Organization on March 11, 2020. As a result of the outbreak, many companies have experienced disruptions in their operations, workforce and markets served, including a significant reduction in the demand for petroleum-based products. The Company's businesses and operations began being adversely impacted by effects of COVID-19 in March of 2020 when circumstances surrounding and responses to the pandemic, including stay-at-home orders, began to materialize in North America. These disruptions had a significant impact on the Company's operating results during the three months ended June 30, 2020 and the Company expects that operations will continue to see an impact. The full extent of the ongoing COVID-19 outbreak and changes in demand for oil and the impact on the Company’s operations is uncertain. A prolonged disruption could have a material adverse impact on financial results and business operations of the Company. In response to the COVID-19 outbreak, the Company has seen increased demand in emergency response services. In particular, the Company is addressing the safety of its customers and communities by providing contagion decontamination services. In conducting these services, employee safety is paramount and the Company has been able to provide appropriate personal protective equipment and support to those performing these services.

SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
SIGNIFICANT ACCOUNTING POLICIES	Jun. 30, 2020
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, 2019. There have been no material changes in these policies or their application except for the changes described below. Landfill Accounting Landfill capacity - During the first six months of 2020, the Company has taken actions to begin the closure of one of the Company's commercial landfill sites. The planned closure will nominally reduce the Company's remaining highly probable airspace. See Note 9, "Closure and Post-Closure Liabilities," for additional information. Government Grants On March 27, 2020, the Coronavirus Aid, Relief and Economic Security Act ("CARES Act") was signed into law in response to the widespread economic impact of the COVID-19 pandemic. On April 11, 2020, the Canadian federal government enacted the COVID-19 Emergency Response Act, No.2, which implemented the Canada Emergency Wage Subsidy ("CEWS"). During the quarter ended June 30, 2020, the Company recorded a benefit of $23.4 million as an offset to the related operating expenses in either cost of revenues or selling, general and administrative expenses for the eligible employee retention credit under the CARES Act and the subsidy under CEWS.

REVENUES

6 Months Ended

Jun. 30, 2020

Revenue from Contract with Customer [Abstract]

REVENUES

The Company generates revenues through its Environmental Services and Safety-Kleen operating segments. The Company's Environmental Services operating segment generally has the following three sources of revenue:

Technical Services—Technical Services revenues 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. 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 from waste that is not yet completely processed and disposed and the related costs are deferred. The deferred revenues and costs are recognized when the related 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 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. More recently demand has increased for 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 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, decoking and pigging, chemical cleaning, high and ultra-high pressure water cleaning, pipeline inspection and coating services, large tank and surface impoundment cleaning, oilfield transport, daylighting, production services and upstream energy services, such as exploration and drilling for industrial oil and gas customers. 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.

The Company's Safety-Kleen operating segment generally has the following two sources of revenue:

Safety-Kleen Environmental Services—Safety-Kleen Environmental Services revenues are generated from providing parts washer services, containerized waste handling and disposal services, oil collection services, vacuum services, direct sales of blended oil products and other complementary services and product sales. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Other products and services include sale of complementary supply products including automotive fluids and shop supplies and other environmental services. 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. 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. Product revenue is recognized upon the transfer of control whereby control transfers when the products are delivered to the customer.

Safety-Kleen Oil—Revenues from Safety-Kleen Oil 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 June 30, 2020
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	403,451	$	228,338	$	(160)	$	631,629
Canada	60,903		17,252		216		78,371
Total third-party revenues	$	464,354	$	245,590	$	56	$	710,000

Sources of Revenue ⁽¹⁾
Technical Services	$	241,929	$	—	$	—	$	241,929
Field and Emergency Response Services	127,353		—		—		127,353
Industrial Services and Other	95,072		—		56		95,128
Safety-Kleen Environmental Services	—		194,872		—		194,872
Safety-Kleen Oil	—		50,718		—		50,718
Total third-party revenues	$	464,354	$	245,590	$	56	$	710,000


	For the Three Months Ended June 30, 2019
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	431,749	$	316,688	$	202	$	748,639
Canada	94,545		25,494		—		120,039
Total third-party revenues	$	526,294	$	342,182	$	202	$	868,678

Sources of Revenue ⁽¹⁾
Technical Services	$	275,908	$	—	$	—	$	275,908
Field and Emergency Response Services	86,722		—		—		86,722
Industrial Services and Other ⁽²⁾	163,664		—		202		163,866
Safety-Kleen Environmental Services	—		216,434		—		216,434
Safety-Kleen Oil	—		125,748		—		125,748
Total third-party revenues	$	526,294	$	342,182	$	202	$	868,678


	For the Six Months Ended June 30, 2020
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	843,465	$	534,871	$	(462)	$	1,377,874
Canada	148,993		41,088		608		190,689
Total third-party revenues	$	992,458	$	575,959	$	146	$	1,568,563

Sources of Revenue ⁽¹⁾
Technical Services	$	517,202	$	—	$	—	$	517,202
Field and Emergency Response Services	233,265		—		—		233,265
Industrial Services and Other	241,991		—		146		242,137
Safety-Kleen Environmental Services	—		409,353		—		409,353
Safety-Kleen Oil	—		166,606		—		166,606
Total third-party revenues	$	992,458	$	575,959	$	146	$	1,568,563


	For the Six Months Ended June 30, 2019
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	819,918	$	603,262	$	796	$	1,423,976
Canada	180,074		45,467		—		225,541
Total third-party revenues	$	999,992	$	648,729	$	796	$	1,649,517

Sources of Revenue⁽¹⁾
Technical Services	$	527,827	$	—	$	—	$	527,827
Field and Emergency Response Services	158,348		—		—		158,348
Industrial Services and Other⁽²⁾	313,817		—		796		314,613

Safety-Kleen Environmental Services	—		423,517		—		423,517
Safety-Kleen Oil	—		225,212		—		225,212
Total third-party revenues	$	999,992	$	648,729	$	796	$	1,649,517

________________

(1) All revenue except oil and oil product sales within Safety-Kleen Oil and product sales within Safety-Kleen Environmental Services, which include various automotive related fluids, shop supplies and direct blended oil sales, are recognized over time. Safety-Kleen Oil and Safety-Kleen Environmental Services product sales are recognized at a point in time.

(2) Third-party revenues of $27,653 and $202 for the three months ended June 30, 2019, respectively, and third-party revenues of $61,708 and $796 for the six months ended June 30, 2019, respectively, previously reported as Oil, Gas and Lodging Services and Other, are now disclosed within Industrial Services and Other based on relative materiality to the business.

Contract Balances


(in thousands)	June 30, 2020		December 31, 2019
Receivables	$	572,373	$	644,738
Contract assets (unbilled receivables)	44,761		56,326
Contract liabilities (deferred revenue)	61,902		73,370

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 generally 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=121604090&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=121604090&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=121604090&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=121604090&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=121604090&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=121604090&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=121604090&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=121604090&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=121604090&loc=SL49130554-203045

+ Details

BUSINESS COMBINATIONS	6 Months Ended
BUSINESS COMBINATIONS	Jun. 30, 2020
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS 2020 Acquisition On April 17, 2020, the Company acquired a privately-owned business for $8.9 million cash consideration. The acquired company expands the Safety-Kleen segment's oil re-refining operations to the northeast United States. In connection with this acquisition, a preliminary goodwill amount of $1.5 million was recognized. 2019 Acquisitions On May 31, 2019, the Company acquired a privately-owned business for $14.8 million cash consideration. The acquired company expands the environmental services and hazardous materials management services of the Company and is included in the Environmental Services segment. In connection with this acquisition, a goodwill amount of $7.4 million was recognized. On March 1, 2019, the Company acquired certain assets of a privately-owned business for $10.4 million cash consideration. The acquired business complements the Safety-Kleen segment's core service offerings, such as used motor oil collection, parts washers, oil filter recycling and vacuum services. In connection with this acquisition, a goodwill amount of $5.2 million was recognized.

INVENTORIES AND SUPPLIES

6 Months Ended

Jun. 30, 2020

Inventory Disclosure [Abstract]

INVENTORIES AND SUPPLIES

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


	June 30, 2020		December 31, 2019
Oil and oil related products	$	77,117	$	75,408
Supplies and drums	118,086		115,128
Solvent and solutions	10,553		9,973

Other	14,052		14,235
Total inventories and supplies	$	219,808	$	214,744

Supplies and drums consist primarily of drums and containers used in providing the Company's products and services, critical spare parts to support the Company's incinerator and re-refinery operations and personal protective equipment. Other inventories consisted primarily of parts washer components, cleaning fluids, absorbents and automotive fluids, such as windshield washer fluid and antifreeze

PROPERTY, PLANT AND EQUIPMENT

6 Months Ended

Jun. 30, 2020

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT AND EQUIPMENT

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


	June 30, 2020		December 31, 2019
Land	$	139,859	$	131,023
Asset retirement costs (non-landfill)	16,102		15,924
Landfill assets	182,287		182,276
Buildings and improvements ⁽¹⁾	499,701		499,159
Camp equipment	153,980		158,277
Vehicles ⁽²⁾	809,790		785,056
Equipment⁽³⁾	1,776,574		1,779,366
Furniture and fixtures	6,860		6,054
Construction in progress	21,040		36,679
	3,606,193		3,593,814
Less - accumulated depreciation and amortization	2,052,385		2,005,663
Total property, plant and equipment, net	$	1,553,808	$	1,588,151

________________

(1) Balances inclusive of gross right-of-use ("ROU") assets classified as finance leases of $8.0 million and $31.0 million, respectively.

(2) Balances inclusive of gross ROU assets classified as finance leases of $37.6 million and $2.4 million, respectively.

(3) June 30, 2020 balance inclusive of gross ROU assets classified as finance leases of $3.3 million.

Depreciation expense, inclusive of landfill and finance lease amortization, was $63.7 million and $129.0 million for the three and six months ended June 30, 2020, respectively. Depreciation expense, inclusive of landfill and finance lease amortization, was $65.5 million and $131.4 million for the three and six months ended June 30, 2019, respectively.

GOODWILL AND OTHER INTANGIBLE ASSETS

6 Months Ended

Jun. 30, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

The changes in goodwill by segment for the six months ended June 30, 2020 were as follows (in thousands):


	Environmental Services		Safety-Kleen		Totals
Balance at January 1, 2020	$	212,531	$	312,482	$	525,013
Increase from current period acquisition	—		1,487		1,487
Measurement period adjustments from prior period acquisitions	23		—		23
Decrease from disposition of businesses	(674)		—		(674)

Foreign currency translation	(1,263)		(1,432)		(2,695)
Balance at June 30, 2020	$	210,617	$	312,537	$	523,154

The Company assesses goodwill for impairment on an annual basis as of December 31 or at an interim date when events or changes in the business environment ("triggering events") would more likely than not reduce the fair value of a reporting unit below its carrying value. During the period ended June 30, 2020, the Company considered the effects of COVID-19 and evolving changes in demand and pricing for oil, but concluded that there were no triggering events requiring an impairment assessment. This conclusion was based on a qualitative analysis incorporating (i) the significant excess fair value that previously existed in each reporting unit and (ii) assessing the current and long-term performance of the Company given the expectation that these negative effects on the operations and cash flows of each reporting unit arising from COVID-19 related disruptions will be short-lived.

The Company continues to evaluate the impact of macroeconomic conditions including, but not limited to, the impact of the COVID-19 pandemic on the Company, customers and the greater economy as well as the impact on trends of oil demand. If these macroeconomic conditions are protracted or result in significant changes in demand for our products and services, a goodwill impairment might be identified and the amount might be material.

As of June 30, 2020 and December 31, 2019, the Company's intangible assets consisted of the following (in thousands):


	June 30, 2020										December 31, 2019
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	182,689	$	90,360	$	92,329	$	184,235	$	87,228	$	97,007
Customer and supplier relationships	388,341		207,604		180,737		401,696		207,884		193,812
Other intangible assets	37,480		32,561		4,919		38,331		33,018		5,313
Total amortizable permits and other intangible assets	608,510		330,525		277,985		624,262		328,130		296,132
Trademarks and trade names	122,463		—		122,463		122,934		—		122,934
Total permits and other intangible assets	$	730,973	$	330,525	$	400,448	$	747,196	$	328,130	$	419,066

Amortization expense of permits and other intangible assets was $8.8 million and $18.0 million in the three and six months ended June 30, 2020, respectively. Amortization expense of permits and other intangible assets was $8.7 million and $18.2 million in the three and six months ended June 30, 2019, respectively.

The expected amortization of the net carrying amount of finite-lived intangible assets at June 30, 2020 was as follows (in thousands):


Years Ending December 31,	Expected Amortization
2020 (six months)	$	16,038
2021	29,858
2022	29,594
2023	25,391
2024	23,919
Thereafter	153,185
	$	277,985

ACCRUED EXPENSES

6 Months Ended

Jun. 30, 2020

Payables and Accruals [Abstract]

ACCRUED EXPENSES

Accrued expenses consisted of the following (in thousands):


	June 30, 2020		December 31, 2019
Accrued insurance	$	72,081	$	74,376
Accrued interest	19,589		21,222
Accrued compensation and benefits	48,427		72,473
Accrued income, real estate, sales and other taxes	54,667		35,749
Interest rate swap liability	38,993		20,840
Accrued other	55,657		51,880
	$	289,414	$	276,540

CLOSURE AND POST-CLOSURE LIABILITIES

6 Months Ended

Jun. 30, 2020

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, 2020 through June 30, 2020 were as follows (in thousands):


	Landfill Retirement Liability		Non-Landfill Retirement Liability		Total
Balance at January 1, 2020	$	39,401	$	36,250	$	75,651
Liabilities assumed in acquisitions	—		265		265

New asset retirement obligations	1,080		—		1,080

Accretion	1,521		1,655		3,176
Changes in estimates recorded to statement of operations	4,503		(36)		4,467
Changes in estimates recorded to balance sheet	129		(53)		76
Expenditures	(1,254)		(491)		(1,745)
Currency translation and other	(249)		(80)		(329)
Balance at June 30, 2020	$	45,131	$	37,510	$	82,641

During the first six months of 2020, the Company has taken actions to begin the closure of one of its commercial landfill sites resulting in a $4.5 million increase to the related closure and post-closure liability. The remaining ten landfill facilities remain active as of June 30, 2020. In the six months ended June 30, 2020, other than this charge, 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 six months of 2020 were discounted at the credit-adjusted risk-free rate of 5.60%.

REMEDIAL LIABILITIES

6 Months Ended

Jun. 30, 2020

Environmental Remediation Obligations [Abstract]

REMEDIAL LIABILITIES

The changes to remedial liabilities from January 1, 2020 through June 30, 2020 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, 2020	$	1,851	$	61,991	$	50,331	$	114,173


Accretion	44		1,265		842		2,151
Changes in estimates recorded to statement of operations	(14)		(330)		1,484		1,140
Expenditures	(30)		(2,171)		(2,158)		(4,359)
Currency translation and other	—		(923)		301		(622)
Balance at June 30, 2020	$	1,851	$	59,832	$	50,800	$	112,483

In the six months ended June 30, 2020, the Company increased its remedial liabilities for a Superfund site by $1.8 million due to a change in the estimate of the related liabilities. This change in estimate was triggered by the receipt of updated regulatory approval requirements for remediation. Other than this charge, there were no significant charges (benefits) resulting from changes in estimates for remedial liabilities.

FINANCING ARRANGEMENTS

6 Months Ended

Jun. 30, 2020

Debt Disclosure [Abstract]

FINANCING ARRANGEMENTS

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


Current Obligations:	June 30, 2020		December 31, 2019
Secured senior term loans ("Term Loans")	$	7,535	$	7,535

Long-Term Obligations:
Secured senior Term Loans due June 30, 2024	$	723,394	$	727,162
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
Revolving credit facility	75,000		—
Long-term obligations, at par	$	1,643,394	$	1,572,162
Unamortized debt issuance costs and premium, net	(16,523)		(18,046)
Long-term obligations, at carrying value	$	1,626,871	$	1,554,116

Financing Activities

As of June 30, 2020 and December 31, 2019, the estimated fair value of the Company’s outstanding long-term obligations, including the current portion, was $1.7 billion and $1.6 billion, respectively. The Company’s estimates of fair value of its long-term obligations, 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 expiring November 1, 2021. On March 31, 2020, the Company drew down $150.0 million on the revolving credit facility in response to the uncertainty surrounding the COVID-19 global pandemic. The Company repaid $75.0 million of that borrowing on June 29, 2020, and the remaining $75.0 million was repaid on July 28, 2020. As of June 30, 2020, the Company had $135.3 million available to borrow under the revolving credit facility and outstanding letters of credit were $142.5 million. At December 31, 2019, $229.2 million was available to borrow and outstanding letters of credit were $146.9 million.

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 rate on the Term Loans is variable, the Company has effectively fixed the interest rate on $350.0 million aggregate principal amount of the 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 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 June 30, 2020 and December 31, 2019, the Company has recorded an interest rate swap liability with a fair value of $39.0 million and $20.8 million, respectively, within accrued expenses 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.

INCOME TAXES	6 Months Ended
INCOME TAXES	Jun. 30, 2020
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 six months ended June 30, 2020 was 29.0% and 34.7%, compared to 30.7% and 37.2%, respectively, for the comparable periods in 2019. As of June 30, 2020 and December 31, 2019, the Company had recorded $6.1 million and $6.4 million, respectively, of liabilities for unrecognized tax benefits and $1.9 million and $1.7 million, respectively, of interest. The Internal Revenue Service ("IRS") completed its examination of the Company’s tax years 2014-2016 and submitted its audit report to the Joint Committee on Taxation ("Joint Committee"). In July 2020, we received notification from the IRS that the Joint Committee has completed its review and taken no exception. No material adjustments were made to the previously filed returns as a result of this process. The Company believes that within the next 12 months uncertain tax positions may be resolved and statutes of limitations will expire which could result in a decrease in the gross amount of unrecognized tax benefits of $1.0 million.

- 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 + Details

EARNINGS PER SHARE

6 Months Ended

Jun. 30, 2020

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						Six Months Ended
	June 30,						June 30,
	2020		2019		2020		2019
Numerator for basic and diluted earnings per share:
Net income	$	29,023	$	36,244	$	40,595	$	37,220

Denominator:
Basic shares outstanding	55,590		55,875		55,673		55,861
Dilutive effect of outstanding stock awards	158		191		209		140
Dilutive shares outstanding	55,748		56,066		55,882		56,001

Basic earnings per share:	$	0.52	$	0.65	$	0.73	$	0.67

Diluted earnings per share:	$	0.52	$	0.65	$	0.73	$	0.66

For the three months ended June 30, 2020 and June 30, 2019, all then outstanding performance awards and restricted stock awards were included in the calculation of diluted earnings per share except for 96,018 and 75,759, respectively, of performance stock awards for which the performance criteria were not attained at the time and 149,460 and 4,623, respectively, of restricted stock awards and performance awards which were excluded as their inclusion would have an antidilutive effect.

For the six months ended June 30, 2020 and June 30, 2019, all then outstanding performance awards and restricted stock awards were included in the calculation of diluted earnings per share except for 96,018 and 75,759, respectively, of performance stock awards for which the performance criteria were not attained at the time and 14,716 and 78,892, respectively, of restricted stock awards which were excluded as their inclusion would have an antidilutive effect.

ACCUMULATED OTHER COMPREHENSIVE LOSS

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

ACCUMULATED OTHER COMPREHENSIVE LOSS

The changes in accumulated other comprehensive loss by component and related tax effects for the six months ended June 30, 2020 were as follows (in thousands):


	Foreign Currency Translation		Unrealized Gains (Losses) on Available-For-Sale Securities		Unrealized Loss on Interest Rate Hedge		Unfunded Pension Liability		Total
Balance at January 1, 2020	$	(187,795)	$	143	$	(20,839)	$	(1,560)	$	(210,051)
Other comprehensive (loss) income before reclassifications and tax impacts	(25,205)		294		(21,382)		—		(46,293)
Amounts reclassified out of accumulated other comprehensive loss	—		—		3,228		—		3,228
Tax gain (loss)	1,349		(62)		—		—		1,287
Other comprehensive (loss) income	(23,856)		232		(18,154)		—		(41,778)
Balance at June 30, 2020	$	(211,651)	$	375	$	(38,993)	$	(1,560)	$	(251,829)

The amount reclassified out of accumulated other comprehensive loss into the consolidated statement of operations, with presentation location, during the three and six months ended June 30, 2020 was as follows (in thousands):


Other Comprehensive Income (Loss) Components	For the Three Months Ended June 30, 2020		For the Six Months Ended June 30, 2020		Location

Unrealized loss on interest rate hedge	$	(2,130)	$	(3,228)	Interest expense, net of interest income

STOCK-BASED COMPENSATION

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

On June 3, 2020, our shareholders approved the Clean Harbor's Inc. 2020 Stock Incentive Plan (the "2020 Plan"), which became effective on that date. The 2020 Plan provides for future awards of up to 2.5 million shares of the Company’s common stock (subject to certain anti-dilution adjustments) in the form of stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards. The 2020 Plan is administered by the Compensation Committee of the Company’s Board of Directors. The Company's previous stock incentive plan (the "2010 Plan") expired on May 10, 2020. In connection with the adoption of the 2020 Plan, no further awards will be made under the 2010 Plan.

Total stock-based compensation cost charged to selling, general and administrative expenses for the three and six months ended June 30, 2020 was $2.8 million and $6.1 million, respectively. Total stock-based compensation cost charged to selling, general and administrative expenses for the three and six months ended June 30, 2019 was $3.8 million and $9.6 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense for the three and six months ended June 30, 2020 was $0.4 million and $1.2 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense for the three and six months ended June 30, 2019 was $0.7 million and $1.8 million, respectively.

Restricted Stock Awards

The following table summarizes information about restricted stock awards for the six months ended June 30, 2020:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2020	522,597	$	59.57
Granted	52,078	59.07
Vested	(147,197)	57.33
Forfeited	(31,640)	58.64
Balance at June 30, 2020	395,838	60.42

As of June 30, 2020, there was $16.5 million of total unrecognized compensation cost arising from restricted stock awards. This cost is expected to be recognized over a weighted average period of 2.3 years. The total fair value of restricted stock vested during the three and six months ended June 30, 2020 was $4.4 million and $9.7 million, respectively. The total fair value of restricted stock vested during the three and six months ended June 30, 2019 was $7.9 million and $11.1 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 typically based on revenue, Adjusted EBITDA margin, Adjusted Free Cash Flow 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 six months ended June 30, 2020:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2020	204,553	$	64.78
Granted	—	—
Vested	(23,222)	55.75
Forfeited	(11,976)	65.71
Balance at June 30, 2020	169,355	65.95

As of June 30, 2020, there was $1.6 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 June 30, 2020 and June 30, 2019. The total fair value of performance awards vested during the six months ended June 30, 2020 and June 30, 2019 was $1.3 million and $2.9 million, respectively.

COMMITMENTS AND CONTINGENCIES	6 Months Ended
COMMITMENTS AND CONTINGENCIES	Jun. 30, 2020
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 June 30, 2020 and December 31, 2019, the Company had recorded reserves of $23.5 million and $26.0 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 June 30, 2020 and December 31, 2019, the $23.5 million and $26.0 million, respectively, of reserves consisted of (i) $17.7 million and $18.4 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) $5.8 million and $7.6 million, respectively, primarily related to federal, state and provincial enforcement actions, which were included in accrued expenses on the consolidated balance sheets. As of June 30, 2020, the principal legal and administrative proceedings in which the Company was involved, or which had been terminated during 2020, 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 June 30, 2020 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 67 proceedings (excluding cases which have been settled but not formally dismissed) as of June 30, 2020, 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 June 30, 2020. From January 1, 2020 to June 30, 2020, three 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 (which, since December 28, 2012, includes Safety-Kleen) 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 130 sites which are subject to or are proposed to become subject to proceedings under federal or state Superfund laws. Of the 130 sites, five (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, 31 are now settled, 78 are currently requiring expenditures on remediation and 16 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 $100,000 at 10 of the 125 third-party 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 and feasibility study for Devil's Swamp under an order issued by the EPA. The Company cannot presently estimate the potential additional liability for the Devil's Swamp cleanup until a final remedy is selected by the EPA with issuance of a Record of Decision. Third-Party Sites. Of the 125 third-party sites at which the Company has been notified it is a PRP or potential PRP or may have indemnification obligations, Clean Harbors has an indemnification agreement at 11 of these sites with ChemWaste, a former subsidiary of Waste Management, Inc., and at six additional of these third-party sites, Safety-Kleen has a similar indemnification agreement with McKesson Corporation. These agreements indemnify the Company (which now includes Safety-Kleen) with respect to any liability at the 17 sites for waste disposed prior to the Company's (or Safety-Kleen's) acquisition of the former subsidiaries of Waste Management and McKesson which had shipped wastes to those sites. Accordingly, Waste Management or McKesson are paying all costs of defending those subsidiaries in those 17 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 two other entities, 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 June 30, 2020 and December 31, 2019, there were 11 and 12 proceedings, respectively, for which the Company reasonably believes that the sanctions could equal or exceed $100,000. The Company believes that the fines or other penalties in these or any of the other regulatory proceedings will, individually or in the aggregate, not have a material effect on its financial condition, results of operations or cash flows.

SEGMENT REPORTING

6 Months Ended

Jun. 30, 2020

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. The Company is managed and reports as two operating segments; (i) the Environmental Services segment and (ii) the Safety-Kleen segment.

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. 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 six months ended June 30, 2020 and June 30, 2019 (in thousands):


	For the Three Months Ended June 30, 2020														For the Three Months Ended June 30, 2019
	Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues
Environmental Services	$	464,354	$	31,171	$	1,389	$	496,914	$	526,294	$	36,206	$	576	$	563,076
Safety-Kleen	245,590		(31,171)		137		214,556		342,182		(36,206)		8		305,984
Corporate Items	56		—		(1,526)		(1,470)		202		—		(584)		(382)
Total	$	710,000	$	—	$	—	$	710,000	$	868,678	$	—	$	—	$	868,678


	For the Six Months Ended June 30, 2020														For the Six Months Ended June 30, 2019
	Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues
Environmental Services	$	992,458	$	68,334	$	2,484	$	1,063,276	$	999,992	$	70,281	$	1,825	$	1,072,098
Safety-Kleen	575,959		(68,334)		143		507,768		648,729		(70,281)		13		578,461
Corporate Items	146		—		(2,627)		(2,481)		796		—		(1,838)		(1,042)
Total	$	1,568,563	$	—	$	—	$	1,568,563	$	1,649,517	$	—	$	—	$	1,649,517

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, depreciation and amortization, net interest expense, loss on early extinguishment of debt, provision for income taxes and other gains, losses or non-cash charges not deemed representative of fundamental segment results and other expense (income), net. Transactions between the segments are accounted for at the Company’s best estimate based on similar transactions with outside customers.

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


	For the Three Months Ended						For the Six Months Ended
	June 30,						June 30,
	2020		2019		2020		2019
Adjusted EBITDA:
Environmental Services	$	138,083	$	117,868	$	246,997	$	207,378
Safety-Kleen	46,589		79,459		107,737		134,252
Corporate Items	(49,192)		(47,502)		(96,664)		(90,142)
Total	135,480		149,825		258,070		251,488
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,766		2,560		5,327		5,134
Depreciation and amortization	72,494		74,217		147,027		149,572

Income from operations	60,220		73,048		105,716		96,782
Other expense (income), net	500		564		2,865		(2,419)

Loss on sale of businesses	184		—		3,258		—
Interest expense, net of interest income	18,654		20,215		37,441		39,979
Income before provision for income taxes	$	40,882	$	52,269	$	62,152	$	59,222

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


	June 30, 2020		December 31, 2019
Property, plant and equipment, net:
Environmental Services	$	904,626	$	939,352
Safety-Kleen	558,597		555,310
Corporate Items	90,585		93,489
Total property, plant and equipment, net	$	1,553,808	$	1,588,151

Goodwill and Permits and other intangibles, net:
Environmental Services
Goodwill	$	210,617	$	212,531
Permits and other intangibles, net	83,465		89,722
Total Environmental Services	294,082		302,253

Safety-Kleen
Goodwill	$	312,537	$	312,482
Permits and other intangibles, net	316,983		329,344
Total Safety-Kleen	629,520		641,826

Total	$	923,602	$	944,079

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


	June 30, 2020		December 31, 2019
United States	$	3,461,132	$	3,413,254
Canada and other foreign	616,497		695,650
Total	$	4,077,629	$	4,108,904

- 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.

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+ Details

SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Jun. 30, 2020
Accounting Policies [Abstract]
Revenues	The Company's Environmental Services operating segment generally has the following three sources of revenue: Technical Services—Technical Services revenues 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. 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 from waste that is not yet completely processed and disposed and the related costs are deferred. The deferred revenues and costs are recognized when the related 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 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. More recently demand has increased for 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 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, decoking and pigging, chemical cleaning, high and ultra-high pressure water cleaning, pipeline inspection and coating services, large tank and surface impoundment cleaning, oilfield transport, daylighting, production services and upstream energy services, such as exploration and drilling for industrial oil and gas customers. 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. The Company's Safety-Kleen operating segment generally has the following two sources of revenue: Safety-Kleen Environmental Services—Safety-Kleen Environmental Services revenues are generated from providing parts washer services, containerized waste handling and disposal services, oil collection services, vacuum services, direct sales of blended oil products and other complementary services and product sales. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Other products and services include sale of complementary supply products including automotive fluids and shop supplies and other environmental services. 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. 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. Product revenue is recognized upon the transfer of control whereby control transfers when the products are delivered to the customer. Safety-Kleen Oil—Revenues from Safety-Kleen Oil 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)

6 Months Ended

Jun. 30, 2020

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue


	For the Three Months Ended June 30, 2020
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	403,451	$	228,338	$	(160)	$	631,629
Canada	60,903		17,252		216		78,371
Total third-party revenues	$	464,354	$	245,590	$	56	$	710,000

Sources of Revenue ⁽¹⁾
Technical Services	$	241,929	$	—	$	—	$	241,929
Field and Emergency Response Services	127,353		—		—		127,353
Industrial Services and Other	95,072		—		56		95,128
Safety-Kleen Environmental Services	—		194,872		—		194,872
Safety-Kleen Oil	—		50,718		—		50,718
Total third-party revenues	$	464,354	$	245,590	$	56	$	710,000


	For the Three Months Ended June 30, 2019
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	431,749	$	316,688	$	202	$	748,639
Canada	94,545		25,494		—		120,039
Total third-party revenues	$	526,294	$	342,182	$	202	$	868,678

Sources of Revenue ⁽¹⁾
Technical Services	$	275,908	$	—	$	—	$	275,908
Field and Emergency Response Services	86,722		—		—		86,722
Industrial Services and Other ⁽²⁾	163,664		—		202		163,866
Safety-Kleen Environmental Services	—		216,434		—		216,434
Safety-Kleen Oil	—		125,748		—		125,748
Total third-party revenues	$	526,294	$	342,182	$	202	$	868,678


	For the Six Months Ended June 30, 2020
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	843,465	$	534,871	$	(462)	$	1,377,874
Canada	148,993		41,088		608		190,689
Total third-party revenues	$	992,458	$	575,959	$	146	$	1,568,563

Sources of Revenue ⁽¹⁾
Technical Services	$	517,202	$	—	$	—	$	517,202
Field and Emergency Response Services	233,265		—		—		233,265
Industrial Services and Other	241,991		—		146		242,137
Safety-Kleen Environmental Services	—		409,353		—		409,353
Safety-Kleen Oil	—		166,606		—		166,606
Total third-party revenues	$	992,458	$	575,959	$	146	$	1,568,563


	For the Six Months Ended June 30, 2019
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	819,918	$	603,262	$	796	$	1,423,976
Canada	180,074		45,467		—		225,541
Total third-party revenues	$	999,992	$	648,729	$	796	$	1,649,517

Sources of Revenue⁽¹⁾
Technical Services	$	527,827	$	—	$	—	$	527,827
Field and Emergency Response Services	158,348		—		—		158,348
Industrial Services and Other⁽²⁾	313,817		—		796		314,613

Safety-Kleen Environmental Services	—		423,517		—		423,517
Safety-Kleen Oil	—		225,212		—		225,212
Total third-party revenues	$	999,992	$	648,729	$	796	$	1,649,517

________________

Schedule of Contract Balances


(in thousands)	June 30, 2020		December 31, 2019
Receivables	$	572,373	$	644,738
Contract assets (unbilled receivables)	44,761		56,326
Contract liabilities (deferred revenue)	61,902		73,370

INVENTORIES AND SUPPLIES (Tables)

6 Months Ended

Jun. 30, 2020

Inventory Disclosure [Abstract]

Schedule of Inventory

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


	June 30, 2020		December 31, 2019
Oil and oil related products	$	77,117	$	75,408
Supplies and drums	118,086		115,128
Solvent and solutions	10,553		9,973

Other	14,052		14,235
Total inventories and supplies	$	219,808	$	214,744

PROPERTY, PLANT AND EQUIPMENT (Tables)

6 Months Ended

Jun. 30, 2020

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

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


	June 30, 2020		December 31, 2019
Land	$	139,859	$	131,023
Asset retirement costs (non-landfill)	16,102		15,924
Landfill assets	182,287		182,276
Buildings and improvements ⁽¹⁾	499,701		499,159
Camp equipment	153,980		158,277
Vehicles ⁽²⁾	809,790		785,056
Equipment⁽³⁾	1,776,574		1,779,366
Furniture and fixtures	6,860		6,054
Construction in progress	21,040		36,679
	3,606,193		3,593,814
Less - accumulated depreciation and amortization	2,052,385		2,005,663
Total property, plant and equipment, net	$	1,553,808	$	1,588,151

________________

(1) Balances inclusive of gross right-of-use ("ROU") assets classified as finance leases of $8.0 million and $31.0 million, respectively.

(2) Balances inclusive of gross ROU assets classified as finance leases of $37.6 million and $2.4 million, respectively.

(3) June 30, 2020 balance inclusive of gross ROU assets classified as finance leases of $3.3 million.

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)

6 Months Ended

Jun. 30, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes to Goodwill

The changes in goodwill by segment for the six months ended June 30, 2020 were as follows (in thousands):


	Environmental Services		Safety-Kleen		Totals
Balance at January 1, 2020	$	212,531	$	312,482	$	525,013
Increase from current period acquisition	—		1,487		1,487
Measurement period adjustments from prior period acquisitions	23		—		23
Decrease from disposition of businesses	(674)		—		(674)

Foreign currency translation	(1,263)		(1,432)		(2,695)
Balance at June 30, 2020	$	210,617	$	312,537	$	523,154

Summary of Indefinite-Lived Intangible Assets

As of June 30, 2020 and December 31, 2019, the Company's intangible assets consisted of the following (in thousands):


	June 30, 2020										December 31, 2019
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	182,689	$	90,360	$	92,329	$	184,235	$	87,228	$	97,007
Customer and supplier relationships	388,341		207,604		180,737		401,696		207,884		193,812
Other intangible assets	37,480		32,561		4,919		38,331		33,018		5,313
Total amortizable permits and other intangible assets	608,510		330,525		277,985		624,262		328,130		296,132
Trademarks and trade names	122,463		—		122,463		122,934		—		122,934
Total permits and other intangible assets	$	730,973	$	330,525	$	400,448	$	747,196	$	328,130	$	419,066

Schedule of Finite-Lived Intangible Assets

As of June 30, 2020 and December 31, 2019, the Company's intangible assets consisted of the following (in thousands):


	June 30, 2020										December 31, 2019
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	182,689	$	90,360	$	92,329	$	184,235	$	87,228	$	97,007
Customer and supplier relationships	388,341		207,604		180,737		401,696		207,884		193,812
Other intangible assets	37,480		32,561		4,919		38,331		33,018		5,313
Total amortizable permits and other intangible assets	608,510		330,525		277,985		624,262		328,130		296,132
Trademarks and trade names	122,463		—		122,463		122,934		—		122,934
Total permits and other intangible assets	$	730,973	$	330,525	$	400,448	$	747,196	$	328,130	$	419,066

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 June 30, 2020 was as follows (in thousands):


Years Ending December 31,	Expected Amortization
2020 (six months)	$	16,038
2021	29,858
2022	29,594
2023	25,391
2024	23,919
Thereafter	153,185
	$	277,985

ACCRUED EXPENSES (Tables)

6 Months Ended

Jun. 30, 2020

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	June 30, 2020		December 31, 2019
Accrued insurance	$	72,081	$	74,376
Accrued interest	19,589		21,222
Accrued compensation and benefits	48,427		72,473
Accrued income, real estate, sales and other taxes	54,667		35,749
Interest rate swap liability	38,993		20,840
Accrued other	55,657		51,880
	$	289,414	$	276,540

CLOSURE AND POST-CLOSURE LIABILITIES (Tables)

6 Months Ended

Jun. 30, 2020

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, 2020 through June 30, 2020 were as follows (in thousands):


	Landfill Retirement Liability		Non-Landfill Retirement Liability		Total
Balance at January 1, 2020	$	39,401	$	36,250	$	75,651
Liabilities assumed in acquisitions	—		265		265

New asset retirement obligations	1,080		—		1,080

Accretion	1,521		1,655		3,176
Changes in estimates recorded to statement of operations	4,503		(36)		4,467
Changes in estimates recorded to balance sheet	129		(53)		76
Expenditures	(1,254)		(491)		(1,745)
Currency translation and other	(249)		(80)		(329)
Balance at June 30, 2020	$	45,131	$	37,510	$	82,641

REMEDIAL LIABILITIES (Tables)

6 Months Ended

Jun. 30, 2020

Environmental Remediation Obligations [Abstract]

Schedule of Changes to Remedial Liabilities

The changes to remedial liabilities from January 1, 2020 through June 30, 2020 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, 2020	$	1,851	$	61,991	$	50,331	$	114,173


Accretion	44		1,265		842		2,151
Changes in estimates recorded to statement of operations	(14)		(330)		1,484		1,140
Expenditures	(30)		(2,171)		(2,158)		(4,359)
Currency translation and other	—		(923)		301		(622)
Balance at June 30, 2020	$	1,851	$	59,832	$	50,800	$	112,483

FINANCING ARRANGEMENTS (Tables)

6 Months Ended

Jun. 30, 2020

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 Obligations:	June 30, 2020		December 31, 2019
Secured senior term loans ("Term Loans")	$	7,535	$	7,535

Long-Term Obligations:
Secured senior Term Loans due June 30, 2024	$	723,394	$	727,162
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
Revolving credit facility	75,000		—
Long-term obligations, at par	$	1,643,394	$	1,572,162
Unamortized debt issuance costs and premium, net	(16,523)		(18,046)
Long-term obligations, at carrying value	$	1,626,871	$	1,554,116

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 835
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 505
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 235
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-Subparagraph (SX 210.4-08.(e),(f))
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 835
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

EARNINGS PER SHARE (Tables)

6 Months Ended

Jun. 30, 2020

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						Six Months Ended
	June 30,						June 30,
	2020		2019		2020		2019
Numerator for basic and diluted earnings per share:
Net income	$	29,023	$	36,244	$	40,595	$	37,220

Denominator:
Basic shares outstanding	55,590		55,875		55,673		55,861
Dilutive effect of outstanding stock awards	158		191		209		140
Dilutive shares outstanding	55,748		56,066		55,882		56,001

Basic earnings per share:	$	0.52	$	0.65	$	0.73	$	0.67

Diluted earnings per share:	$	0.52	$	0.65	$	0.73	$	0.66

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Schedule of Accumulated Other Comprehensive Loss

The changes in accumulated other comprehensive loss by component and related tax effects for the six months ended June 30, 2020 were as follows (in thousands):


	Foreign Currency Translation		Unrealized Gains (Losses) on Available-For-Sale Securities		Unrealized Loss on Interest Rate Hedge		Unfunded Pension Liability		Total
Balance at January 1, 2020	$	(187,795)	$	143	$	(20,839)	$	(1,560)	$	(210,051)
Other comprehensive (loss) income before reclassifications and tax impacts	(25,205)		294		(21,382)		—		(46,293)
Amounts reclassified out of accumulated other comprehensive loss	—		—		3,228		—		3,228
Tax gain (loss)	1,349		(62)		—		—		1,287
Other comprehensive (loss) income	(23,856)		232		(18,154)		—		(41,778)
Balance at June 30, 2020	$	(211,651)	$	375	$	(38,993)	$	(1,560)	$	(251,829)

Schedule of Reclassification Out of Accumulated Other Comprehensive Income


Other Comprehensive Income (Loss) Components	For the Three Months Ended June 30, 2020		For the Six Months Ended June 30, 2020		Location

Unrealized loss on interest rate hedge	$	(2,130)	$	(3,228)	Interest expense, net of interest income

STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Restricted Stock Awards

The following table summarizes information about restricted stock awards for the six months ended June 30, 2020:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2020	522,597	$	59.57
Granted	52,078	59.07
Vested	(147,197)	57.33
Forfeited	(31,640)	58.64
Balance at June 30, 2020	395,838	60.42

Schedule of Performance Stock Awards

The following table summarizes information about performance stock awards for the six months ended June 30, 2020:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2020	204,553	$	64.78
Granted	—	—
Vested	(23,222)	55.75
Forfeited	(11,976)	65.71
Balance at June 30, 2020	169,355	65.95

SEGMENT REPORTING (Tables)

6 Months Ended

Jun. 30, 2020

Segment Reporting [Abstract]

Schedule of Segment Reporting Information

The following table reconciles third-party revenues to direct revenues for the three and six months ended June 30, 2020 and June 30, 2019 (in thousands):


	For the Three Months Ended June 30, 2020														For the Three Months Ended June 30, 2019
	Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues
Environmental Services	$	464,354	$	31,171	$	1,389	$	496,914	$	526,294	$	36,206	$	576	$	563,076
Safety-Kleen	245,590		(31,171)		137		214,556		342,182		(36,206)		8		305,984
Corporate Items	56		—		(1,526)		(1,470)		202		—		(584)		(382)
Total	$	710,000	$	—	$	—	$	710,000	$	868,678	$	—	$	—	$	868,678


	For the Six Months Ended June 30, 2020														For the Six Months Ended June 30, 2019
	Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues		Third-party revenues		Intersegment revenues, net		Corporate Items, net		Direct revenues
Environmental Services	$	992,458	$	68,334	$	2,484	$	1,063,276	$	999,992	$	70,281	$	1,825	$	1,072,098
Safety-Kleen	575,959		(68,334)		143		507,768		648,729		(70,281)		13		578,461
Corporate Items	146		—		(2,627)		(2,481)		796		—		(1,838)		(1,042)
Total	$	1,568,563	$	—	$	—	$	1,568,563	$	1,649,517	$	—	$	—	$	1,649,517

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


	June 30, 2020		December 31, 2019
Property, plant and equipment, net:
Environmental Services	$	904,626	$	939,352
Safety-Kleen	558,597		555,310
Corporate Items	90,585		93,489
Total property, plant and equipment, net	$	1,553,808	$	1,588,151

Goodwill and Permits and other intangibles, net:
Environmental Services
Goodwill	$	210,617	$	212,531
Permits and other intangibles, net	83,465		89,722
Total Environmental Services	294,082		302,253

Safety-Kleen
Goodwill	$	312,537	$	312,482
Permits and other intangibles, net	316,983		329,344
Total Safety-Kleen	629,520		641,826

Total	$	923,602	$	944,079

Schedule of Reconciliation to Consolidated Statements of Income from Adjusted EBITDA

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


	For the Three Months Ended						For the Six Months Ended
	June 30,						June 30,
	2020		2019		2020		2019
Adjusted EBITDA:
Environmental Services	$	138,083	$	117,868	$	246,997	$	207,378
Safety-Kleen	46,589		79,459		107,737		134,252
Corporate Items	(49,192)		(47,502)		(96,664)		(90,142)
Total	135,480		149,825		258,070		251,488
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,766		2,560		5,327		5,134
Depreciation and amortization	72,494		74,217		147,027		149,572

Income from operations	60,220		73,048		105,716		96,782
Other expense (income), net	500		564		2,865		(2,419)

Loss on sale of businesses	184		—		3,258		—
Interest expense, net of interest income	18,654		20,215		37,441		39,979
Income before provision for income taxes	$	40,882	$	52,269	$	62,152	$	59,222

Total Assets by Geographical Area

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


	June 30, 2020		December 31, 2019
United States	$	3,461,132	$	3,413,254
Canada and other foreign	616,497		695,650
Total	$	4,077,629	$	4,108,904

SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions	3 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions	Jun. 30, 2020 USD ($)
Accounting Policies [Abstract]
Benefit amount under CARES Act and CEWS	$ 23.4

REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 710,000	$ 868,678	$ 1,568,563	$ 1,649,517
Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	241,929	275,908	517,202	527,827
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	127,353	86,722	233,265	158,348
Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	95,128	163,866	242,137	314,613
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	194,872	216,434	409,353	423,517
Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	50,718	125,748	166,606	225,212
United States
Disaggregation of Revenue [Line Items]
Total revenues	631,629	748,639	1,377,874	1,423,976
Canada
Disaggregation of Revenue [Line Items]
Total revenues	78,371	120,039	190,689	225,541
Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	496,914	563,076	1,063,276	1,072,098
Safety-Kleen
Disaggregation of Revenue [Line Items]
Total revenues	214,556	305,984	507,768	578,461
Operating segments \| Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	464,354	526,294	992,458	999,992
Operating segments \| Environmental Services \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	241,929	275,908	517,202	527,827
Operating segments \| Environmental Services \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	127,353	86,722	233,265	158,348
Operating segments \| Environmental Services \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	95,072	163,664	241,991	313,817
Operating segments \| Environmental Services \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Environmental Services \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Environmental Services \| Oil, Gas and Lodging Services
Disaggregation of Revenue [Line Items]
Total revenues		27,653		61,708
Operating segments \| Environmental Services \| United States
Disaggregation of Revenue [Line Items]
Total revenues	403,451	431,749	843,465	819,918
Operating segments \| Environmental Services \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	60,903	94,545	148,993	180,074
Operating segments \| Safety-Kleen
Disaggregation of Revenue [Line Items]
Total revenues	245,590	342,182	575,959	648,729
Operating segments \| Safety-Kleen \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Safety-Kleen \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Safety-Kleen \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments \| Safety-Kleen \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	194,872	216,434	409,353	423,517
Operating segments \| Safety-Kleen \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	50,718	125,748	166,606	225,212
Operating segments \| Safety-Kleen \| United States
Disaggregation of Revenue [Line Items]
Total revenues	228,338	316,688	534,871	603,262
Operating segments \| Safety-Kleen \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	17,252	25,494	41,088	45,467
Corporate
Disaggregation of Revenue [Line Items]
Total revenues	56	202	146	796
Corporate \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	56	202	146	796
Corporate \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Oil, Gas and Lodging Services
Disaggregation of Revenue [Line Items]
Total revenues		202		796
Corporate \| United States
Disaggregation of Revenue [Line Items]
Total revenues	(160)	202	(462)	796
Corporate \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	$ 216	$ 0	$ 608	$ 0

REVENUES - Contract Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Receivables	$ 572,373	$ 644,738
Contract assets (unbilled receivables)	44,761	56,326
Contract liabilities (deferred revenue)	$ 61,902	$ 73,370

REVENUES - Narrative (Details)	6 Months Ended
REVENUES - Narrative (Details)	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Contract liability, recognition period	3 months

BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands				6 Months Ended
BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands	Apr. 17, 2020	May 31, 2019	Mar. 01, 2019	Jun. 30, 2020
Business Acquisition [Line Items]
Goodwill recognized				$ 1,487
2020 Acquisitions
Business Acquisition [Line Items]
Purchase price	$ 8,900
Goodwill recognized	$ 1,500
2019 Acquisitions
Business Acquisition [Line Items]
Purchase price		$ 14,800	$ 10,400
Goodwill recognized		$ 7,400	$ 5,200

INVENTORIES AND SUPPLIES (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Oil and oil related products	$ 77,117	$ 75,408
Supplies and drums	118,086	115,128
Solvent and solutions	10,553	9,973
Other	14,052	14,235
Total inventories and supplies	$ 219,808	$ 214,744

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 3,606,193	$ 3,593,814
Less - accumulated depreciation and amortization	2,052,385	2,005,663
Total property, plant and equipment, net	1,553,808	1,588,151
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	139,859	131,023
Asset retirement costs (non-landfill)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	16,102	15,924
Landfill assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	182,287	182,276
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	499,701	499,159
Right-of-Use assets, finance leases	8,000	31,000
Camp equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	153,980	158,277
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	809,790	785,056
Right-of-Use assets, finance leases	37,600	2,400
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,776,574	1,779,366
Right-of-Use assets, finance leases	3,300
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,860	6,054
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 21,040	$ 36,679

PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Depreciation inclusive of amortization	$ 63.7	$ 65.5	$ 129.0	$ 131.4

GOODWILL AND OTHER INTANGIBLE ASSETS - Rollforward of Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2020	$ 525,013
Increase from current period acquisition	1,487
Measurement period adjustments from prior period acquisitions	23
Decrease from disposition of businesses	(674)
Foreign currency translation	(2,695)
Balance at June 30, 2020	523,154
Environmental Services
Goodwill [Roll Forward]
Balance at January 1, 2020	212,531
Increase from current period acquisition	0
Measurement period adjustments from prior period acquisitions	23
Decrease from disposition of businesses	(674)
Foreign currency translation	(1,263)
Balance at June 30, 2020	210,617
Safety-Kleen
Goodwill [Roll Forward]
Balance at January 1, 2020	312,482
Increase from current period acquisition	1,487
Measurement period adjustments from prior period acquisitions	0
Decrease from disposition of businesses	0
Foreign currency translation	(1,432)
Balance at June 30, 2020	$ 312,537

GOODWILL AND OTHER INTANGIBLE ASSETS - Amortizable Other Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	$ 608,510	$ 624,262
Accumulated Amortization	330,525	328,130
Finite-lived intangible assets, net	277,985	296,132
Total permits and other intangible assets, Cost	730,973	747,196
Total permits and other intangible assets, Net	400,448	419,066
Trademarks and trade names
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Trademarks and trade names	122,463	122,934
Permits
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	182,689	184,235
Accumulated Amortization	90,360	87,228
Finite-lived intangible assets, net	92,329	97,007
Customer and supplier relationships
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	388,341	401,696
Accumulated Amortization	207,604	207,884
Finite-lived intangible assets, net	180,737	193,812
Other intangible assets
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	37,480	38,331
Accumulated Amortization	32,561	33,018
Finite-lived intangible assets, net	$ 4,919	$ 5,313

GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of permits and other intangible assets	$ 8.8	$ 8.7	$ 18.0	$ 18.2

GOODWILL AND OTHER INTANGIBLE ASSETS - Expected Future Amortization (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
2020 (six months)	$ 16,038
2021	29,858
2022	29,594
2023	25,391
2024	23,919
Thereafter	153,185
Finite-lived intangible assets, net	$ 277,985	$ 296,132

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued insurance	$ 72,081	$ 74,376
Accrued interest	19,589	21,222
Accrued compensation and benefits	48,427	72,473
Accrued income, real estate, sales and other taxes	54,667	35,749
Interest rate swap liability	38,993	20,840
Accrued other	55,657	51,880
Total accrued expenses	$ 289,414	$ 276,540

CLOSURE AND POST-CLOSURE LIABILITIES (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) facility
Changes to post-closure liabilities
Balance at January 1, 2020	$ 75,651
Liabilities assumed in acquisitions	265
New asset retirement obligations	1,080
Accretion	3,176
Changes in estimates recorded to statement of operations	4,467
Changes in estimates recorded to balance sheet	76
Expenditures	(1,745)
Currency translation and other	(329)
Balance at June 30, 2020	$ 82,641
Number of active landfill facilities \| facility	10
Credit-adjusted risk-free rate	5.60%
Landfill Retirement Liability
Changes to post-closure liabilities
Balance at January 1, 2020	$ 39,401
Liabilities assumed in acquisitions	0
New asset retirement obligations	1,080
Accretion	1,521
Changes in estimates recorded to statement of operations	4,503
Changes in estimates recorded to balance sheet	129
Expenditures	(1,254)
Currency translation and other	(249)
Balance at June 30, 2020	45,131
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Balance at January 1, 2020	36,250
Liabilities assumed in acquisitions	265
New asset retirement obligations	0
Accretion	1,655
Changes in estimates recorded to statement of operations	(36)
Changes in estimates recorded to balance sheet	(53)
Expenditures	(491)
Currency translation and other	(80)
Balance at June 30, 2020	$ 37,510

REMEDIAL LIABILITIES (Details) $ in Thousands	6 Months Ended
REMEDIAL LIABILITIES (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2020	$ 114,173
Accretion	2,151
Changes in estimates recorded to statement of operations	1,140
Expenditures	(4,359)
Currency translation and other	(622)
Balance at June 30, 2020	112,483
Remedial Liabilities for Landfill Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2020	1,851
Accretion	44
Changes in estimates recorded to statement of operations	(14)
Expenditures	(30)
Currency translation and other	0
Balance at June 30, 2020	1,851
Increase of remedial liabilities	1,800
Remedial Liabilities for Inactive Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2020	61,991
Accretion	1,265
Changes in estimates recorded to statement of operations	(330)
Expenditures	(2,171)
Currency translation and other	(923)
Balance at June 30, 2020	59,832
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at January 1, 2020	50,331
Accretion	842
Changes in estimates recorded to statement of operations	1,484
Expenditures	(2,158)
Currency translation and other	301
Balance at June 30, 2020	$ 50,800

FINANCING ARRANGEMENTS - Summary of Financing Arrangements (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Current portion of long-term obligations	$ 7,535	$ 7,535
Long-term obligations	1,643,394	1,572,162
Unamortized debt issuance costs and premium, net	(16,523)	(18,046)
Long-term obligations, at carrying value	1,626,871	1,554,116
Secured debt \| Term Loan Agreement
Debt Instrument [Line Items]
Current portion of long-term obligations	7,535	7,535
Long-term obligations	723,394	727,162
Unsecured debt \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument [Line Items]
Long-term obligations	$ 545,000	545,000
Interest rate (as a percentage)	4.875%
Unsecured debt \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument [Line Items]
Long-term obligations	$ 300,000	300,000
Interest rate (as a percentage)	5.125%
Line of Credit \| Revolving credit facility
Debt Instrument [Line Items]
Long-term obligations	$ 75,000	$ 0

FINANCING ARRANGEMENTS - Narrative (Details) - USD ($)				6 Months Ended
FINANCING ARRANGEMENTS - Narrative (Details) - USD ($)	Jul. 28, 2020	Jun. 29, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Debt fair value				$ 1,700,000,000		$ 1,600,000,000
Borrowing from revolving credit facility				150,000,000	$ 0
Repayments of borrowings				75,000,000	$ 0
Available to borrow and outstanding letters of credit				135,300,000		229,200,000
Outstanding letters of credit				$ 142,500,000		146,900,000
Effective interest rate percentage				4.67%
Interest rate swap, liability				$ 39,000,000.0		$ 20,800,000
Term Loans with Interest Rate Swap Agreements
Debt Instrument [Line Items]
Debt outstanding				350,000,000.0
Revolving credit facility \| Line of Credit
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity				400,000,000.0
Borrowing from revolving credit facility			$ 150,000,000.0
Repayments of borrowings		$ 75,000,000.0
Revolving credit facility \| Line of Credit \| Subsequent Event
Debt Instrument [Line Items]
Repayments of borrowings	$ 75,000,000.0
Interest Rate Swap
Debt Instrument [Line Items]
Notional amount of interest rate swap agreements				$ 350,000,000.0
Interest rate percentage				2.92%

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
INCOME TAXES (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Effective income tax rate	29.00%	30.70%	34.70%	37.20%
Unrecognized tax benefits	$ 6.1		$ 6.1		$ 6.4
Interest on unrecognized tax benefits	1.9		1.9		$ 1.7
Reduction in unrecognized tax benefits from expiring statue of limitations within next 12 months	$ 1.0		$ 1.0

EARNINGS PER SHARE - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator for basic and diluted earnings per share:
Net income	$ 29,023	$ 11,572	$ 36,244	$ 976	$ 40,595	$ 37,220
Denominator:
Basic shares outstanding (in shares)	55,590		55,875		55,673	55,861
Dilutive effect of outstanding stock awards (in shares)	158		191		209	140
Dilutive shares outstanding (in shares)	55,748		56,066		55,882	56,001
Basic earnings per share (in USD per share)	$ 0.52		$ 0.65		$ 0.73	$ 0.67
Diluted earnings per share (in USD per share)	$ 0.52		$ 0.65		$ 0.73	$ 0.66

- 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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+ Details

EARNINGS PER SHARE - Narrative (Details) - shares	3 Months Ended		6 Months Ended
EARNINGS PER SHARE - Narrative (Details) - shares	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Performance stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earning per share (in shares)	96,018	75,759	96,018	75,759
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)	149,460	4,623	14,716	78,892

ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance beginning of period	$ 1,205,805	$ 1,269,813	$ 1,171,965	$ 1,169,756	$ 1,269,813	$ 1,169,756
Other comprehensive (loss) income before reclassifications and tax impacts					(46,293)
Amounts reclassified out of accumulated other comprehensive loss					3,228
Tax gain (loss)					1,287
Other comprehensive income (loss), net of tax	17,528	(59,306)	5,076	4,024	(41,778)	9,100
Balance ending of period	1,253,971	1,205,805	1,209,467	1,171,965	1,253,971	1,209,467
Foreign Currency Translation
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance beginning of period		(187,795)			(187,795)
Other comprehensive (loss) income before reclassifications and tax impacts					(25,205)
Amounts reclassified out of accumulated other comprehensive loss					0
Tax gain (loss)					1,349
Other comprehensive income (loss), net of tax					(23,856)
Balance ending of period	(211,651)				(211,651)
Unrealized Gains (Losses) on Available-For-Sale Securities
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance beginning of period		143			143
Other comprehensive (loss) income before reclassifications and tax impacts					294
Amounts reclassified out of accumulated other comprehensive loss					0
Tax gain (loss)					(62)
Other comprehensive income (loss), net of tax					232
Balance ending of period	375				375
Unrealized Loss on Interest Rate Hedge
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance beginning of period		(20,839)			(20,839)
Other comprehensive (loss) income before reclassifications and tax impacts					(21,382)
Amounts reclassified out of accumulated other comprehensive loss					3,228
Tax gain (loss)					0
Other comprehensive income (loss), net of tax					(18,154)
Balance ending of period	(38,993)				(38,993)
Unfunded Pension Liability
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance beginning of period		(1,560)			(1,560)
Other comprehensive (loss) income before reclassifications and tax impacts					0
Amounts reclassified out of accumulated other comprehensive loss					0
Tax gain (loss)					0
Other comprehensive income (loss), net of tax					0
Balance ending of period	(1,560)				(1,560)
Total
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance beginning of period	(269,357)	(210,051)	(219,347)	(223,371)	(210,051)	(223,371)
Other comprehensive income (loss), net of tax	17,528	(59,306)	5,076	4,024
Balance ending of period	$ (251,829)	$ (269,357)	$ (214,271)	$ (219,347)	$ (251,829)	$ (214,271)

ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassified Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Unrealized loss on interest rate hedge \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net of interest income	$ (2,130)	$ (3,228)

STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 03, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2.8	$ 3.8	$ 6.1	$ 9.6
Income tax benefit	$ 0.4	$ 0.7	$ 1.2	$ 1.8
2020 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares originally authorized for issuance (in shares)					2,500,000

STOCK-BASED COMPENSATION - Restricted Stock Awards (Details) - Restricted stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Number of Shares
Beginning balance (in shares)			522,597
Granted (in shares)			52,078
Vested (in shares)			(147,197)
Forfeited (in shares)			(31,640)
Ending balance (in shares)	395,838		395,838
Weighted Average Grant-Date Fair Value
Beginning of period (in USD per share)			$ 59.57
Granted (in USD per share)			59.07
Vested (in USD per share)			57.33
Forfeited (in USD per share)			58.64
End of period (in USD per share)	$ 60.42		$ 60.42
Unrecognized compensation cost	$ 16.5		$ 16.5
Period for recognition (in years)			2 years 3 months 18 days
Fair value restricted stock	$ 4.4	$ 7.9	$ 9.7	$ 11.1

STOCK-BASED COMPENSATION - Performance Stock Awards (Details) - Performance stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Number of Shares
Beginning balance (in shares)			204,553
Granted (in shares)			0
Vested (in shares)	0	0	(23,222)
Forfeited (in shares)			(11,976)
Ending balance (in shares)	169,355		169,355
Weighted Average Grant-Date Fair Value
Beginning of period (in USD per share)			$ 64.78
Granted (in USD per share)			0
Vested (in USD per share)			55.75
Forfeited (in USD per share)			65.71
End of period (in USD per share)	$ 65.95		$ 65.95
Unrecognized compensation cost	$ 1.6		$ 1.6
Fair value restricted stock			$ 1.3	$ 2.9

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	6 Months Ended	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Jun. 30, 2020 USD ($) proceeding claim site	Dec. 31, 2012 CAD ($)	Dec. 31, 1999 municipality	Dec. 31, 1968 permit	Dec. 31, 2019 USD ($) proceeding
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 23,500,000				$ 26,000,000.0
Number of proceedings as defendant \| proceeding	67
Number of product liability claims settled or dismissed \| claim	3
Legal and Administrative Proceedings
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 17,700,000				18,400,000
Ville Mercier
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
Contingencies [Line Items]
Number of sites owned by third party excluded from cleanup or related liabilities	130
Number of sites owned by the entity subject to proceedings under federal or state superfund laws	5
Number of sites owned by third parties	125
Number of sites for which environmental remediation expense is settled	31
Third party sites requiring expenditure on remediation	78
Number of sites not currently requiring expenditures on remediation	16
Number of sites, potential liability exceeds substantial quota	10
Notices received from owners of third parties sites seeking indemnifications from the company	17
Superfund Proceedings \| Minimum
Contingencies [Line Items]
Minimum potential liability \| $	$ 100,000
ChemWaste
Contingencies [Line Items]
Indemnification agreement with third party sites	11
Kleen Performance Products
Contingencies [Line Items]
Notices received from owners of third parties sites seeking indemnifications from the company	6
Federal and State Enforcement Actions
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 5,800,000				$ 7,600,000
Number of proceedings as defendant \| proceeding	11				12
Federal and State Enforcement Actions \| Minimum
Contingencies [Line Items]
Minimum potential liability \| $	$ 100,000				$ 100,000

SEGMENT REPORTING - Narrative (Details)	6 Months Ended
SEGMENT REPORTING - Narrative (Details)	Jun. 30, 2020 segment
Segment Reporting [Abstract]
Number of operating segments	2

SEGMENT REPORTING - Third Party Revenues to Direct Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 710,000	$ 868,678	$ 1,568,563	$ 1,649,517
Corporate
Segment Reporting Information [Line Items]
Total revenues	56	202	146	796
Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(1,526)	(584)	(2,627)	(1,838)
Operating and Corporate non-segment
Segment Reporting Information [Line Items]
Total revenues	(1,470)	(382)	(2,481)	(1,042)
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	496,914	563,076	1,063,276	1,072,098
Environmental Services \| Operating segments
Segment Reporting Information [Line Items]
Total revenues	464,354	526,294	992,458	999,992
Environmental Services \| Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	31,171	36,206	68,334	70,281
Environmental Services \| Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	1,389	576	2,484	1,825
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	214,556	305,984	507,768	578,461
Safety-Kleen \| Operating segments
Segment Reporting Information [Line Items]
Total revenues	245,590	342,182	575,959	648,729
Safety-Kleen \| Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(31,171)	(36,206)	(68,334)	(70,281)
Safety-Kleen \| Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	$ 137	$ 8	$ 143	$ 13

- 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

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+ Details

SEGMENT REPORTING - Adjusted EBITDA Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 135,480	$ 149,825	$ 258,070	$ 251,488
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,766	2,560	5,327	5,134
Depreciation and amortization	72,494	74,217	147,027	149,572
Income from operations	60,220	73,048	105,716	96,782
Other expense (income), net	500	564	2,865	(2,419)
Loss on sale of businesses	184	0	3,258	0
Interest expense, net of interest income	18,654	20,215	37,441	39,979
Income before provision for income taxes	40,882	52,269	62,152	59,222
Operating segments \| Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	138,083	117,868	246,997	207,378
Operating segments \| Safety-Kleen
Segment Reporting Information [Line Items]
Adjusted EBITDA	46,589	79,459	107,737	134,252
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (49,192)	$ (47,502)	$ (96,664)	$ (90,142)

SEGMENT REPORTING - Assets by Reportable Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,553,808	$ 1,588,151
Goodwill	523,154	525,013
Permits and other intangibles, net	400,448	419,066
Goodwill and permits and other intangibles, net	923,602	944,079
Environmental Services
Segment Reporting Information [Line Items]
Goodwill	210,617	212,531
Safety-Kleen
Segment Reporting Information [Line Items]
Goodwill	312,537	312,482
Operating segments \| Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	904,626	939,352
Goodwill	210,617	212,531
Permits and other intangibles, net	83,465	89,722
Goodwill and permits and other intangibles, net	294,082	302,253
Operating segments \| Safety-Kleen
Segment Reporting Information [Line Items]
Property, plant and equipment, net	558,597	555,310
Goodwill	312,537	312,482
Permits and other intangibles, net	316,983	329,344
Goodwill and permits and other intangibles, net	629,520	641,826
Corporate
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 90,585	$ 93,489

SEGMENT REPORTING - Total Assets by Geographical Area (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 4,077,629	$ 4,108,904
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	3,461,132	3,413,254
Canada and other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 616,497	$ 695,650

- 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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