Inventory Disclosure [Abstract] INVENTORIES AND SUPPLIES Inventory Disclosure [Text Block] Environmental Remediation Obligations [Abstract] Site Contingency [Table] Site Contingency [Table] Environmental Remediation Site [Axis] Environmental Remediation Site [Axis] Environmental Remediation Site [Domain] Environmental Remediation Site [Domain] Remedial Liabilities for Landfill Sites Remedial Liabilities for Landfill Sites [Member] This element represents the details that pertain to the remedial liability for landfill sites. Remedial Liabilities for Inactive Sites Remedial Liabilities for Inactive Sites [Member] This element represents the details that pertain to the remedial liabilities for inactive sites. Remedial Liabilities (Including Superfund) for Non-Landfill Operations Remedial Liabilities (Including Superfund) for Non-Landfill Operations [Member] This element represents the details that pertain to the remedial liabilities for non-landfill sites. Remedial liabilities Site Contingency [Line Items] Accrual for Environmental Loss Contingencies [Roll Forward] Accrual for Environmental Loss Contingencies [Roll Forward] Balance at January 1, 2020 Accrual for Environmental Loss Contingencies Accretion Accrual for Environmental Loss Contingencies, Charges to Expense for New Losses Changes in estimates recorded to statement of operations Accrual for Environmental Loss Contingencies, Revision in Estimates Expenditures Accrual for Environmental Loss Contingencies, Payments Currency translation and other Accrual for Environmental Loss Contingencies, Increase (Decrease) for Currency Translation and Other The increase or decrease in the accrual for environmental loss contingencies, during the reporting period that is related to currency translations and other adjustments. Balance at March 31, 2020 Segment Reporting [Abstract] Number of operating segments Number of Operating Segments Debt Disclosure [Abstract] FINANCING ARRANGEMENTS Debt Disclosure [Text Block] Payables and Accruals [Abstract] Accrued insurance Accrued Insurance, Current Accrued interest Interest Payable, Current Accrued compensation and benefits Employee-related Liabilities, Current Accrued income, real estate, sales and other taxes Taxes Payable, Current Accrued other Other Accrued Liabilities, Current Total accrued expenses Accrued Liabilities, Current Accounting Policies [Abstract] Revenues Revenue from Contract with Customer [Policy Text Block] Earnings Per Share [Abstract] EARNINGS PER SHARE Earnings Per Share [Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Short-term marketable securities Marketable Securities, Current Accounts receivable, net of allowances aggregating $42,781 and $38,711, respectively Accounts Receivable, after Allowance for Credit Loss, Current Unbilled accounts receivable Unbilled Accounts Receivable, Current The aggregate amount of unbilled receivables due for services rendered or to be rendered at the financial statement date, which are usually due within one year (or one business cycle). Deferred costs Debt Issuance Costs, Current, Net Inventories and supplies Prepaid Supplies Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property, plant and equipment, net Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Other assets: Other Assets, Noncurrent [Abstract] Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Goodwill Goodwill Permits and other intangibles, net Intangible Assets, Net (Excluding Goodwill) Other Other Assets, Noncurrent Total other assets Assets, Noncurrent, Excluding Property, Plant and Equipment Sum of the carrying amounts as of the balance sheet date of all assets (excluding property, plant and equipment) that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Total assets Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Current portion of long-term obligations Long-term Debt, Current Maturities Accounts payable Accounts Payable, Current Deferred revenue Contract with Customer, Liability, Current Accrued expenses Current portion of closure, post-closure and remedial liabilities Accrued Capping, Closure, Post Closure and Remedial Liabilities, Current The amount of estimated costs accrued as of the balance sheet date to comply with regulatory requirements pertaining to the retirement of a waste management facility (such as a landfill or waste treatment facility) and to remediate one or more sites. Represents the portion that will be paid within one year. Current portion of operating lease liabilities Operating Lease, Liability, Current Total current liabilities Liabilities, Current Other liabilities: Other Liabilities, Noncurrent [Abstract] Closure and post-closure liabilities, less current portion of $4,333 and $7,283, respectively Accrued Capping, Closure, Post-closure and Environmental Costs, Noncurrent Remedial liabilities, less current portion of $11,898 and $16,018, respectively Accrued Environmental Loss Contingencies, Noncurrent Long-term obligations, less current portion Long-term Debt, Excluding Current Maturities Operating lease liabilities, less current portion Operating Lease, Liability, Noncurrent Deferred taxes, unrecognized tax benefits and other long-term liabilities Unrecognized Tax Benefits and Other Long-term Liabilities, Noncurrent The noncurrent portion of the amount that is recognized for the unrecognized tax benefits and other long-term liabilities as of the balance sheet date. Total other liabilities Liabilities, Noncurrent Commitments and contingent liabilities (See Note 16) Commitments and Contingencies Stockholders’ equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Authorized 80,000,000 shares; issued and outstanding 55,554,925 and 55,797,734 shares, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated earnings Retained Earnings (Accumulated Deficit) Total stockholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders’ equity Liabilities and Equity Numerator for basic and diluted earnings per share: Numerator for Basic and Diluted Earnings Per Share [Abstract] -- None. No documentation exists for this element. -- Net income Net Income (Loss) Attributable to Parent Denominator: Denominator for Basic and Diluted Earnings Per Share [Abstract] -- None. No documentation exists for this element. -- Basic shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Dilutive effect of outstanding stock awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Dilutive shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Basic earnings per share (in USD per share) Earnings Per Share, Basic Diluted earnings per share (in USD per share) Earnings Per Share, Diluted Share-based Payment Arrangement [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Performance stock awards Performance Stock Awards [Member] Performance Stock Awards [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Ending balance (in shares) Weighted Average Grant-Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Beginning of period (in USD per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in USD per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vested (in USD per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in USD per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value End of period (in USD per share) Unrecognized compensation cost Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Fair value restricted stock Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Commitments and Contingencies Disclosure [Abstract] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating segments Operating Segments [Member] Corporate Items Corporate, Non-Segment [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Environmental Services Environmental Services [Member] Environmental Services [Member] Safety-Kleen Safety-Kleen [Member] Safety-Kleen [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States UNITED STATES Canada CANADA Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Technical Services Technical Services [Member] This element represents the Technical Services segment of the entity. Field and Emergency Response Services Field and Emergency Response [Member] Field and Emergency Response [Member] Industrial Services and Other Industrial Services And Other [Member] Industrial Services And Other [Member] Safety-Kleen Environmental Services Safetly-Kleen Environmental Services [Member] Safetly-Kleen Environmental Services [Member] Safety-Kleen Oil Safety-Kleen Oil [Member] Safety-Kleen Oil [Member] Oil, Gas and Lodging Services Oil, Gas and Lodging Services [Member] Oil, Gas and Lodging Services [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Total third party revenues Revenue from Contract with Customer, Excluding Assessed Tax Property, Plant and Equipment [Abstract] Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Environmental Contingencies [Table] Environmental Contingencies [Table] Discloses the specific components (such as the nature, name, and date) of the environmental contingencies and gives the possible estimates, or states that a reasonable estimate cannot be made. Contingencies by Nature of Contingency [Axis] Contingencies by Nature of Contingency [Axis] Quantifies and describes each contingency that exists as of the balance sheet date, by nature of the probable or possible estimates. Contingency Nature [Domain] Contingency Nature [Domain] An existing condition, situation, or a set of circumstances, which involve uncertainty as to the possible outcomes to an enterprise that will ultimately be resolved, when one or more future events occur or fail to occur. Resolution of the uncertainty may confirm the incurrence of a loss or profit or the incurrence of a liability. Legal and Administrative Proceedings Legal and Administrative Proceedings [Member] Represents the actual or potential liabilities that are related to the legal and administrative proceedings. Ville Mercier Ville Mercier [Member] Represents the details that pertain to the Ville Mercier. Superfund Proceedings Superfund Proceedings [Member] Represents the indemnification obligations under federal or state Superfund laws. ChemWaste Certain Other Third Party Sites [member] Represents the details that pertain to Certain Other Third Party Sites. Kleen Performance Products Kleen Performance Products [Member] Kleen Performance Products Federal and State Enforcement Actions Federal and State Enforcement Actions [Member] The regulatory proceedings that are relating primarily to waste treatment, storage or disposal facilities. Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Contingencies [Line Items] Contingencies [Line Items] -- None. No documentation exists for this element. -- Recorded reserves for actual or probable liabilities Loss Contingency Accrual Number of permits issued by government, for dumping organic liquid Number of Permits Issued by Government to Dump Organic Liquid The number of permits that are granted by the government in relation to environmental liabilities. Number of neighboring municipalities filing separate legal proceedings against the Mercier Subsidiary and the Government of Quebec Number of Neighboring Municipalities Filing Separate Legal Proceedings This element represents the number of municipalities other than Ville Mercier that filed legal proceedings against the Mercier Subsidiary. General damages sought Loss Contingency, General Damages Sought, Value Loss Contingency, General Damages Sought, Value Punitive damages sought Loss Contingency, Punitive Damages Sought, Value Loss Contingency, Punitive Damages Sought, Value Number of proceedings as defendant Loss Contingency, Pending Claims, Number Number of product liability claims settled or dismissed Loss Contingency, Claims Settled and Dismissed, Number Number of sites owned by third party excluded from cleanup or related liabilities Site Contingency, Number of Sites The number of sites that are subject to proceedings under federal or state superfund laws brought against the company or against third parties for which the company may have certain indemnification obligations. Number of sites owned by the entity subject to proceedings under federal or state superfund laws Site Contingency, Number of Sites Owned by Entity The number of sites that are subject to proceedings under federal or state superfund laws that are owned by the entity. Number of sites owned by third parties Site Contingency, Number of Sites Owned by Third Party The number of sites owned by third parties subject to proceedings under federal or state Superfund laws for which the company or the prior owners shipped wastes. Number of sites for which environmental remediation expense is settled Site Contingency, Environmental Remediation Expense Settled Number of Sites Owned by Third Party The number of sites owned by the third party for which environmental remediation expense is settled. Third party sites requiring expenditure on remediation Site Contingency, Environmental Remediation Expense Number of Sites Owned by Third Party The number of sites for which environmental remediation expense is incurred subject to proceedings under federal or state superfund laws owned by third party. Number of sites not currently requiring expenditures on remediation Site Contingency, Not Requiring Environmental Remediation Expense Number of Sites Owned by Third Party The number of sites owned by the third party for which environmental remediation expense is not required. Minimum potential liability Loss Contingency, Estimate of Possible Loss Number of sites, potential liability exceeds substantial quota Number of Sites, Potential Liability Exceeds Substantial Quota Number of Sites, Potential Liability Exceeds Substantial Quota Indemnification agreement with third party sites Site Contingency, Indemnification Agreement Number of Sites Owned by Third Party The number of sites for which the company has an indemnification agreement from the third party seller. Notices received from owners of third parties sites seeking indemnifications from the company Site Contingency, Notice Received Number of Sites Owned by Third Party The number of notices received from owners of third party sites related to the CSD assets seeking indemnification from the company. Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Property, plant and equipment, net Property, Plant and Equipment, Net Goodwill and permits and other intangibles, net Intangible Assets, Net (Including Goodwill) Accrued expenses Schedule of Accrued Liabilities [Table Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving credit facility Revolving Credit Facility [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Secured debt Secured Debt [Member] Unsecured debt Unsecured Debt [Member] Line of Credit Line of Credit [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Term Loan Agreement Term Loan Agreement [Member] Term Loan Agreement [Member] Unsecured senior notes, at 4.875%, due July 15, 2027 (2027 Notes) Senior Unsecured Notes due 2027 [Member] Senior Unsecured Notes due 2027 [Member] Unsecured senior notes, at 5.125%, due July 15, 2029 (2029 Notes) Senior Unsecured Notes due 2029 [Member] Senior Unsecured Notes due 2029 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term obligations Long-term Debt, Gross Unamortized debt issuance costs and premium, net Debt Issuance Costs, Net Long-term obligations, at carrying value Interest rate (as a percentage) Debt Instrument, Interest Rate, Stated Percentage Stock-based compensation Share-based Payment Arrangement, Expense Income tax benefit Share-based Payment Arrangement, Expense, Tax Benefit Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Finite-lived and Indefinite-lived Intangible Assets [Table] Schedule of Finite-lived and Indefinite-lived Intangible Assets [Table] Schedule of Finite-lived and Indefinite-lived Intangible Assets [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Permits Permits [Member] The description that pertains to the permits. Customer and supplier relationships Customer Relationships [Member] Other intangible assets Other Intangible Assets [Member] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trademarks and trade names Trademarks and Trade Names [Member] Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items] Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items] [Line Items] for Schedule of Finite-lived and Indefinite-lived Intangible Assets [Table] Cost Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Finite-Lived Intangible Assets, Net Trademarks and trade names Indefinite-lived Intangible Assets (Excluding Goodwill) Total permits and other intangible assets, Cost Intangible Assets, Gross (Excluding Goodwill) Total permits and other intangible assets, Net SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Canada and other foreign Non-US [Member] Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Total assets REMEDIAL LIABILITIES Environmental Loss Contingency Disclosure [Text Block] Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Contract Balances Contract with Customer, Asset and Liability [Table Text Block] Summary of restricted stock awards Nonvested Restricted Stock Shares Activity [Table Text Block] Summary of performance stock awards Schedule of Nonvested Performance-based Units Activity [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Accumulated Earnings Retained Earnings [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance beginning of period Balance beginning of period (in shares) Shares, Issued Net income Other comprehensive (loss) income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Stock-based compensation Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Issuance of common stock for restricted share vesting, net of employee tax withholdings Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Repurchases of common stock Stock Repurchased and Retired During Period, Value Repurchases of common stock (in shares) Stock Repurchased and Retired During Period, Shares Balance ending of period Balance ending of period (in shares) 2020 (nine months) Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2024 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Business Combinations [Abstract] BUSINESS COMBINATIONS Business Combination Disclosure [Text Block] GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill and Intangible Assets Disclosure [Text Block] Income Tax Disclosure [Abstract] INCOME TAXES Income Tax Disclosure [Text Block] Cover [Abstract] Document Type Document Type Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Schedule of changes to goodwill Schedule of Goodwill [Table Text Block] Summary of indefinite-lived intangible assets Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Schedule of finite-lived intangible assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule of expected amortization for the net carrying amount of finite lived intangible assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Common stock, par value (in USD per share) Common Stock, Par or Stated Value Per Share SEGMENT REPORTING Segment Reporting Disclosure [Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Restricted stock awards Restricted Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive shares excluded from computation of earning per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Allowance for doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal) Amortization of deferred financing costs and debt discount Amortization of Debt Issuance Costs and Discounts Accretion of environmental liabilities Accretion of Environmental Liabilities This element includes accretion expenditure that pertains to asset retirement obligations and environmental remediation. Changes in environmental liability estimates Other Increase (Decrease) in Environmental Liabilities Other expense (income), net Other Noncash Income (Expense) Stock-based compensation Share-based Payment Arrangement, Noncash Expense Loss on sale of businesses Gain (Loss) on Disposition of Business Environmental expenditures Payments for Environmental Liabilities Changes in assets and liabilities, net of acquisitions: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable and unbilled accounts receivable Increase (Decrease) in Accounts Receivable Inventories and supplies Increase (Decrease) in Inventories Other current and non-current assets Increase (Decrease) in Other Operating Assets Accounts payable Increase (Decrease) in Accounts Payable Other current and long-term liabilities Increase (Decrease) in Other Operating Liabilities Net cash from operating activities Net Cash Provided by (Used in) Operating Activities Cash flows used in investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Additions to property, plant and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from sale and disposal of fixed assets Proceeds from Sale of Productive Assets Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Proceeds from sale of businesses, net of transactional costs Proceeds from Divestiture of Businesses Additions to intangible assets including costs to obtain or renew permits Additions To Intangible Assets Including Costs To Obtain Or Renew Permits Additions To Intangible Assets Including Costs To Obtain Or Renew Permits Proceeds from sale of available-for-sale securities Proceeds from Sale of Debt Securities, Available-for-sale Purchases of available-for-sale securities Payments to Acquire Debt Securities, Available-for-sale Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from (used in) financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Change in uncashed checks Increase (Decrease) in Outstanding Checks, Financing Activities Tax payments related to withholdings on vested restricted stock Payment, Tax Withholding, Share-based Payment Arrangement Repurchases of common stock Payments for Repurchase of Common Stock Payments on finance lease Finance Lease, Principal Payments Principal payments on debt Repayments of Unsecured Debt Borrowing from revolving credit facility Proceeds from Lines of Credit Net cash from (used in) financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate change on cash Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental information: Supplemental Cash Flow Information [Abstract] Cash payments for interest and income taxes: Cash Payments for Interest and Income Taxes [Abstract] Description and amounts of long lived assets and liabilities held for sale. Disclosure may include the description of the facts and circumstances leading to the expected disposal, manner and timing of disposal, the carrying value of the assets and liabilities held for sale, the gain or loss recognized in the income statement and the income statement caption that includes that gain or loss. Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activities Income taxes paid Income Taxes Paid, Net Non-cash investing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Property, plant and equipment accrued Noncash or Part Noncash Acquisition, Value of Assets Acquired ROU assets obtained in exchange for operating lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability, Including Transfers Right-of-Use Asset Obtained in Exchange for Operating Lease Liability, Including Transfers ROU assets obtained in exchange for finance lease liabilities Right-of-Use Asset Obtained in Exchange for Finance Lease Liability, Including Transfers Right-of-Use Asset Obtained in Exchange for Finance Lease Liability, Including Transfers STOCK-BASED COMPENSATION Share-based Payment Arrangement [Text Block] Schedule of Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Reconciliation to consolidated statements of income from adjusted EBITDA Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Total assets by geographical area Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Oil and oil related products Energy Related Inventory, Crude Oil, Products and Merchandise Supplies and drums Energy Related Inventory Supplies and Drums Energy Related Inventory Supplies and Drums Solvent and solutions Energy Related Inventory, Chemicals Other Energy Related Inventory Other Energy Related Inventory and Supplies Other Total inventories and supplies PROPERTY, PLANT AND EQUIPMENT Property, Plant and Equipment Disclosure [Text Block] Schedule of Inventory Schedule of Inventory, Current [Table Text Block] Summary of the entity's financial arrangements Schedule of Long-term Debt Instruments [Table Text Block] ACCRUED EXPENSES Accrued Expenses Disclosure [Text Block] The entire disclosure for accrued expenses at the end of the reporting period. Depreciation inclusive of amortization Depreciation Inclusive of Amortization Depreciation Inclusive of Amortization Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] 2019 Acquisitions 2019 Acquisitions [Member] 2019 Acquisitions [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Purchase price Business Combination, Consideration Transferred Goodwill recognized Goodwill, Acquired During Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Period for recognition (in years) Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Unrecognized tax benefits Unrecognized Tax Benefits Interest on unrecognized tax benefits Unrecognized Tax Benefits, Interest on Income Taxes Accrued Reduction in unrecognized tax benefits from expiring statue of limitations within next 12 months Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit Account receivable, allowances aggregating Accounts Receivable, Allowance for Credit Loss, Current Closure and post-closure liabilities, current portion Accrued Capping, Closure, Post-closure and Environmental Costs Remedial liabilities, current portion Accrued Environmental Loss Contingencies, Current Common stock, authorized shares (in shares) Common Stock, Shares Authorized Common stock, issued shares (in shares) Common Stock, Shares, Issued Common stock, outstanding shares (in shares) Common Stock, Shares, Outstanding Adjusted EBITDA Income (Loss) from Continuing Operations before Interest, Tax, Depreciation and Amortization, Net This element represents the income or loss from continuing operations before interest, taxes, depreciation and amortization to the economic entity. Reconciliation to Consolidated Statements of Operations: Reconciliation Between Adjusted EBITDA and Income Statement [Abstract] Reconciliation Between Adjusted EBITDA and Income Statement [Abstract] Income from operations Operating Income (Loss) Other expense (income), net Other Nonoperating Income (Expense) Loss on sale of businesses Interest expense, net of interest income Interest Income (Expense), Nonoperating, Net Income before provision for income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Schedule of Goodwill [Table] Schedule of Goodwill [Table] Environmental Services Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Balance at January 1, 2020 Measurement period adjustments from prior period acquisitions Goodwill, Purchase Accounting Adjustments Decrease from disposition of businesses Goodwill, Written off Related to Sale of Business Unit Foreign currency translation Goodwill, Foreign Currency Translation Gain (Loss) Balance at March 31, 2020 Statement of Comprehensive Income [Abstract] Net income Other comprehensive (loss) income, net of tax: Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax [Abstract] Unrealized (losses) gains on available-for-sale securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Unrealized loss on interest rate hedge Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Reclassification adjustment for losses on interest rate hedge included in net income Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Other comprehensive (loss) income, net of tax Comprehensive (loss) income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income Statement [Abstract] Interest income Investment Income, Interest Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest Rate Swap Interest Rate Swap [Member] Term Loans with Interest Rate Swap Agreements Term Loans with Interest Rate Swap Agreements [Member] Term Loans with Interest Rate Swap Agreements [Member] Debt fair value Long-term Debt, Fair Value Revolving credit facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Amount drew down Debt outstanding Long-term Debt Available to borrow and outstanding letters of credit Line of Credit Facility, Remaining Borrowing Capacity Outstanding letters of credit Letters of Credit Outstanding, Amount Notional amount of interest rate swap agreements Derivative, Notional Amount Interest rate percentage Debt Instrument, Basis Spread on Variable Rate Effective interest rate percentage Debt Instrument, Interest Rate, Effective Percentage Derivative liability Derivative Liability Receivables Contract assets (unbilled receivables) Contract liabilities (deferred revenue) Reconciliation of basic and diluted earnings per share computations Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Safety-Kleen Intersegment revenues, net Intersegment Eliminations [Member] Corporate Items, net Segment Reconciling Items [Member] Operating and Corporate non-segment Operating Segments And Corporate Non Segment [Member] Operating Segments And Corporate Non Segment [Member] Total revenues Equity [Abstract] Schedule of accumulated other comprehensive loss Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Reclassification out of accumulated other comprehensive income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Service Service [Member] Product Product [Member] Revenues: Revenues [Abstract] Cost of revenues: (exclusive of items shown separately below) Cost of Revenue [Abstract] Total cost of revenues Cost of Goods and Services Sold Selling, general and administrative expenses Selling, General and Administrative Expense Other (expense) income, net Loss on sale of businesses Interest expense, net of interest income of $998 and $926, respectively Provision for income taxes Income Tax Expense (Benefit) Net income Earnings per share: Basic (in USD per share) Diluted (in USD per share) Shares used to compute earnings per share - Basic (in shares) Shares used to compute earnings per share - Diluted (in shares) Organization, Consolidation and Presentation of Financial Statements [Abstract] BASIS OF PRESENTATION Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Contract liability, recognition period Contract With Customer, Liability, Recognition In Subsequent Period Contract With Customer, Liability, Recognition In Subsequent Period ACCUMULATED OTHER COMPREHENSIVE LOSS Comprehensive Income (Loss) Note [Text Block] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Foreign Currency Translation Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Unrealized (Losses) Gains on Available-For-Sale Securities AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Unrealized Loss on Interest Rate Hedge Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Unfunded Pension Liability Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Total Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Components of Other Accumulated Income, Net of Tax [Roll Forward] Other comprehensive loss before reclassifications OCI, before Reclassifications, before Tax, Attributable to Parent Amounts reclassified out of accumulated other comprehensive loss Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Tax gain Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Table] Unrealized loss on interest rate hedge Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Interest expense, net of interest income Interest Income (Expense), Net Asset Retirement Obligation Disclosure [Abstract] CLOSURE AND POST-CLOSURE LIABILITIES Asset Retirement Obligation Disclosure [Text Block] REVENUES Revenue from Contract with Customer [Text Block] Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Long-Lived Tangible Asset [Axis] Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Domain] Property, Plant and Equipment, Type [Domain] Land Land [Member] Asset retirement costs (non-landfill) Asset Retirement Obligation Costs [Member] Landfill assets Landfill [Member] Buildings and improvements Buildings And Improvement, Including Finance Leases ROU Assets [Member] Buildings And Improvement, Including Finance Leases ROU Assets [Member] Buildings and improvements, finance lease [Member] Buildings And Improvements, Finance Lease [Member] Buildings And Improvements, Finance Lease [Member] Camp equipment Camp Equipment [Member] Represents the industrial lodging facilities that are utilized in the entity's Industrial Services segment to provide lodging services to companies in the refinery and petrochemical industries. Vehicles Vehicles, Including Finance Lease ROU Assets [Member] Vehicles, Including Finance Lease ROU Assets [Member] Vehicles, finance lease Vehicles, Finance Lease [Member] Vehicles, Finance Lease [Member] Equipment Equipment [Member] Furniture and fixtures Furniture and Fixtures [Member] Construction in progress Construction in Progress [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Finance Lease, Right-of-Use Asset, Before Accumulated Amortization Finance Lease, Right-of-Use Asset, Before Accumulated Amortization Finance Lease, Right-of-Use Asset, Before Accumulated Amortization Property, plant and equipment, gross Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Before Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Before Accumulated Depreciation And Amortization Less - accumulated depreciation and amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Accumulated Depreciation And Amortization Total property, plant and equipment, net Amortization of permits and other intangible assets Amortization of Intangible Assets Closure and Post-closure Liabilities [Table] Closure and Post-closure Liabilities [Table] The schedule that reflects each closure and post-closure liabilities, during the period. Closure and Post-closure Liabilities [Axis] Closure and Post-closure Liabilities [Axis] The information about each closure and post-closure liabilities during the period. Closure and Post-closure Liabilities [Domain] Closure and Post-closure Liabilities [Domain] Closure and Post-closure Liabilities [Domain] Landfill Retirement Liability Landfill Retirement Liability [Member] Represents the asset retirement obligations for landfill liability. Non-Landfill Retirement Liability Non-Landfill Retirement Liability [Member] Represents the asset retirement obligations for non-landfill liability. CLOSURE AND POST-CLOSURE LIABILITIES Closure and Post Closure Liabilities [Line Items] -- None. No documentation exists for this element. -- Changes to post-closure liabilities Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Balance at January 1, 2020 Asset Retirement Obligation New asset retirement obligations Asset Retirement Obligation, Liabilities Incurred Accretion Asset Retirement Obligation, Accretion Expense Changes in estimates recorded to statement of operations Asset Retirement Obligation, Changes Recorded in Statement of Income The amount of change in the asset retirement obligation, during the current period, for changes in estimates recorded in the statement of income. Expenditures Asset Retirement Obligation, Liabilities Settled Currency translation and other Asset Retirement Obligation, Foreign Currency Translation Gain (Loss) Balance at March 31, 2020 Number of active landfill facilities Number Of Active Landfill Facilities Number Of Active Landfill Facilities Credit-adjusted risk-free rate Asset Retirement Obligations Discount Rate Asset Retirement Obligations Discount Rate Changes to remedial liabilities Schedule of Environmental Loss Contingencies by Site [Table Text Block] Schedule of closure and post-closure liabilities Schedule of Change in Asset Retirement Obligation [Table Text Block]