Clean Harbors (CLH) 10-Q 1 May 19 2019 Q1 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	CLEAN HARBORS INC
Entity Central Index Key	0000822818
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		55,870,615

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 167,371	$ 226,507
Short-term marketable securities	57,477	52,856
Accounts receivable, net of allowances aggregating $37,409 and $44,315, respectively	613,507	606,952
Unbilled accounts receivable	42,513	54,794
Deferred costs	20,515	18,770
Inventories and supplies	200,814	199,479
Prepaid expenses and other current assets	45,925	42,800
Total current assets	1,148,122	1,202,158
Property, plant and equipment, net	1,588,613	1,561,978
Other assets:
Operating lease right-of-use asset	170,550
Goodwill	517,910	514,189
Permits and other intangibles, net	438,958	441,875
Other	17,901	18,121
Total other assets	1,145,319	974,185
Total assets	3,882,054	3,738,321
Current liabilities:
Current portion of long-term obligations	7,535	7,535
Accounts payable	242,260	276,461
Deferred revenue	67,557	61,843
Accrued expenses	208,386	233,405
Current portion of closure, post-closure and remedial liabilities	27,914	23,034
Current portion of operating lease liability	43,858
Total current liabilities	597,510	602,278
Other liabilities:
Closure and post-closure liabilities, less current portion of $12,337 and $9,592, respectively	62,084	60,339
Remedial liabilities, less current portion of $15,577 and $13,442, respectively	103,384	107,575
Long-term obligations, less current portion	1,564,005	1,565,021
Operating lease liability, less current portion	128,689
Deferred taxes, unrecognized tax benefits and other long-term liabilities	254,417	233,352
Total other liabilities	2,112,579	1,966,287
Commitments and contingent liabilities (See Note 16)
Stockholders’ equity:
Authorized 80,000,000; shares issued and outstanding 55,827,714 and 55,847,261 shares, respectively	558	558
Additional paid-in capital	652,624	655,415
Accumulated other comprehensive loss	(219,347)	(223,371)
Accumulated earnings	738,130	737,154
Total stockholders’ equity	1,171,965	1,169,756
Total liabilities and stockholders’ equity	$ 3,882,054	$ 3,738,321

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 37,409	$ 44,315
Closure and post-closure liabilities, current portion	12,337	9,592
Remedial liabilities, current portion	$ 15,577	$ 13,442
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)	55,827,714	55,847,261
Common stock, outstanding shares (in shares)	55,827,714	55,847,261

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Total revenues	$ 780,839	$ 749,778
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	564,364	546,425
Selling, general and administrative expenses	114,812	115,088
Accretion of environmental liabilities	2,574	2,430
Depreciation and amortization	75,355	74,844
Income from operations	23,734	10,991
Other income (expense), net	2,983	(299)
Interest expense, net of interest income of $926 and $764, respectively	(19,764)	(20,270)
Income (loss) before provision for income taxes	6,953	(9,578)
Provision for income taxes	5,977	3,053
Net income (loss)	$ 976	$ (12,631)
Earnings (loss) per share:
Basic (in USD per share)	$ 0.02	$ (0.22)
Diluted (in USD per share)	$ 0.02	$ (0.22)
Shares used to compute loss per share - Basic (in shares)	55,848	56,457
Shares used to compute loss per share - Diluted (in shares)	56,082	56,457
Service
Revenues:
Total revenues	$ 656,658	$ 619,719
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	463,483	447,649
Product
Revenues:
Total revenues	124,181	130,059
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 100,881	$ 98,776

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Interest income	$ 926	$ 764

UNAUDITED CONSOLIDATED STATEM_3

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 976	$ (12,631)
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale securities (net of tax of $31 and $80, respectively)	143	(195)
Unrealized loss on interest rate hedge	(5,017)	0
Reclassification adjustment for losses on interest rate hedge included in net income (loss) (net of taxes of $0 and $0, respectively)	358	0
Foreign currency translation adjustments	8,540	(16,551)
Other comprehensive income (loss)	4,024	(16,746)
Comprehensive income (loss)	$ 5,000	$ (29,377)

UNAUDITED CONSOLIDATED STATEM_4

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Unrealized (losses) gains on available-for-sale securities, taxes	$ 31	$ 80
Reclassification adjustment for gains on available-for-sale securities included in net (loss) income taxes	$ 0	$ 0

UNAUDITED CONSOLIDATED STATEM_5

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 976	$ (12,631)
Adjustments to reconcile net income (loss) to net cash from operating activities:
Depreciation and amortization	75,355	74,844
Allowance for doubtful accounts	(3,425)	2,303
Amortization of deferred financing costs and debt discount	1,000	916
Accretion of environmental liabilities	2,574	2,430
Changes in environmental liability estimates	(774)	(562)
Deferred income taxes	0	(5)
Stock-based compensation	5,809	3,077
Other (income) expense, net	(2,983)	299
Environmental expenditures	(3,264)	(2,425)
Changes in assets and liabilities, net of acquisitions
Accounts receivable and unbilled accounts receivable	12,086	(14,769)
Inventories and supplies	(832)	(5,625)
Other current and non-current assets	(11,738)	(2,923)
Accounts payable	(27,956)	9,714
Other current and long-term liabilities	(17,088)	(2,740)
Net cash from operating activities	29,740	51,903
Cash flows used in investing activities:
Additions to property, plant and equipment	(58,947)	(44,242)
Proceeds from sale and disposal of fixed assets	4,321	798
Acquisitions, net of cash acquired	(14,870)	(120,000)
Additions to intangible assets including costs to obtain or renew permits	(1,132)	(1,245)
Proceeds from sale of available-for-sale securities	8,600	3,264
Purchases of available-for-sale securities	(12,941)
Purchases of available-for-sale securities		(3,003)
Net cash used in investing activities	(74,969)	(164,428)
Cash flows used in financing activities:
Change in uncashed checks	(4,769)	(3,843)
Tax payments related to withholdings on vested restricted stock	(2,276)	(548)
Repurchases of common stock	(6,324)	(14,264)
Payments on finance lease	(115)	0
Principal payments on debt	(1,884)	(1,000)
Net cash used in financing activities	(15,368)	(19,655)
Effect of exchange rate change on cash	1,461	(867)
Decrease in cash and cash equivalents	(59,136)	(133,047)
Cash and cash equivalents, beginning of period	226,507	319,399
Cash and cash equivalents, end of period	167,371	186,352
Cash payments for interest and income taxes:
Interest paid	8,712	14,676
Income taxes paid	967	1,999
Non-cash investing activities:
Property, plant and equipment accrued	13,002	$ 17,911
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	13,554
Operating cash flows from finance lease	321
Financing cash flows from finance lease	115
ROU assets obtained in exchange for new operating lease liabilities	(3,896)
ROU asset obtained in exchange for new finance lease liability	$ 23,027

UNAUDITED CONSOLIDATED STATEM_6

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 at beginning of period at Dec. 31, 2017	$ 1,188,202	$ 565	$ 686,962	$ (172,407)	$ 673,082
Balance beginning of period (in shares) at Dec. 31, 2017		56,501
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(12,631)				(12,631)
Other comprehensive income	(16,746)			(16,746)
Stock-based compensation	3,077		3,077
Issuance of restricted shares, net of shares remitted and tax withholdings	(548)		(548)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		24
Repurchases of common stock	$ (14,264)	$ (3)	(14,261)
Repurchases of common stock (in shares)	(280)	(280)
Balance at end of period at Mar. 31, 2018	$ 1,145,526	$ 562	675,230	(189,153)	658,887
Balance ending of period (in shares) at Mar. 31, 2018		56,245
Balance at beginning of period at Dec. 31, 2018	1,169,756	$ 558	655,415	(223,371)	737,154
Balance beginning of period (in shares) at Dec. 31, 2018		55,847
Increase (Decrease) in Stockholders' Equity
Net income (loss)	976				976
Other comprehensive income	4,024			4,024
Stock-based compensation	5,809		5,809
Issuance of restricted shares, net of shares remitted and tax withholdings	(2,276)	$ 1	(2,277)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		78
Repurchases of common stock	$ (6,324)	$ (1)	(6,323)
Repurchases of common stock (in shares)	(97)	(97)
Balance at end of period at Mar. 31, 2019	$ 1,171,965	$ 558	$ 652,624	$ (219,347)	$ 738,130
Balance ending of period (in shares) at Mar. 31, 2019		55,828

UNAUDITED CONSOLIDATED STATEM_7

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Common stock, par value (in USD per share)	$ 0.01	$ 0.01	$ 0.01

BASIS OF PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2019
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, 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 connection with the financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 .

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES The Company's significant accounting policies are described in Note 2, "Significant Accounting Policies," and Note 3, "Revenues," in the Company's Annual Report on Form 10-K for the year ended December 31, 2018 . There have been no material changes in these policies or their application except for the changes described below. Recent Accounting Pronouncements Standards implemented In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842) . The amendment increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The Company adopted Topic 842 on January 1, 2019 using the modified retrospective method of adoption. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company's historical accounting methodology pursuant to ASC 840, Leases . As permitted under the transition guidance, the Company elected to apply the package of three practical expedients for all existing leases which, among other things, allowed us to maintain the lease classification for all existing leases at the adoption date. The adoption of Topic 842 resulted in the recognition of right-of-use (“ROU”) assets of $185.5 million and total current and noncurrent lease liabilities of $188.5 million at adoption. Additionally, Topic 842 required new and expanded disclosures to enable users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The standard did not have a material impact on the consolidated statements of operations or cash flows. Leases The Company’s leases predominately relate to real estate and equipment such as vehicles and industrial equipment utilized in operations as well as rail cars utilized in connection with the Company’s transportation needs. Contracts are reviewed at inception to determine if the arrangement is a lease and, if so, whether it is an operating or finance lease. For all of its leases, the Company has elected not to separate lease and nonlease components, such as common area maintenance. The Company generally enters into real estate leases with five to ten-year terms and non-real estate leases with two to seven-year terms. In the normal course of business, the Company also enters into short-term leases having terms of less than one-year. These leases are generally equipment leases entered into for short periods of time (e.g. daily, weekly or monthly), and done so to satisfy immediate and/or short-term operational needs of the business which can arise based upon the nature of particular services performed or seasonality factors. The Company has elected not to recognize ROU assets and lease liabilities for these short-term leases. Expense for all such short-term leases is disclosed as short-term lease cost as shown in Note 17, "Leases." Operating and finance leases with terms exceeding one year are recognized as ROU assets and lease liabilities and measured based on the present value of the future lease payments over the lease term at commencement date. When applicable, the ROU asset includes any lease payments made at or before the commencement date and initial direct costs incurred and is reduced by lease incentives received under the lease agreement, if any. Certain of the Company's real estate leases contain escalating future lease payments. Escalating lease payments that are based upon explicit amounts contained in the lease or an index (e.g., consumer price index) are included in its determination of future lease payments to determine the ROU asset and lease liability recognized at the commencement date. Any differences in the future lease payments from initial recognition are not anticipated to be material and will be recorded as variable lease cost in the period incurred. The variable lease cost will also include the Company’s portion of property tax, utilities and common area maintenance. A significant portion of the Company’s real estate lease agreements include renewal periods at the Company’s option. The Company includes these renewal periods in the lease term only when renewal is reasonably certain based upon facts and circumstances specific to the lease and known by the Company. The Company uses its incremental borrowing rate on collateralized debt based on the information available at the lease commencement date in determining the present value of future lease payments as the implicit rate is typically not readily determinable.

REVENUES

REVENUES	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES Revenue Recognition The Company generates services and product revenues through the following operating segments: Environmental Services and Safety-Kleen. The Company recognizes revenue when control of the promised goods or services is transferred to the Company's customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Product revenues are recognized when the products are delivered and control transfers to the customer. Nature of Goods and Services The majority of the Company’s contracts are for services, which are recognized based on time and materials incurred at contractually agreed-upon rates. The Company’s payment terms vary by the type and location of its customers and the products or services offered. The periods between invoicing and when payments are due are not significant. Any amounts billed to customers related to shipping and handling are classified as revenue and the Company's shipping and handling costs are included in costs of revenues. In the course of the Company's operations, it collects sales tax and other excise taxes from its customers and recognizes a current liability which is then relieved when the taxes are remitted to the appropriate governmental authorities. The Company excludes sales and other excise taxes that it collects from customers from its revenues. Disaggregation of Revenue The following table presents the Company’s third-party revenues disaggregated by revenue source (in thousands): For the Three Months Ended March 31, 2019 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 388,169 $ 286,574 $ 594 $ 675,337 Canada 85,529 19,973 — 105,502 Total third-party revenues $ 473,698 $ 306,547 $ 594 $ 780,839 Sources of Revenue (1) Technical Services $ 251,919 $ — $ — $ 251,919 Field and Emergency Response Services 71,626 — — 71,626 Industrial Services 116,098 — — 116,098 Oil, Gas and Lodging Services and Other 34,055 — 594 34,649 Safety-Kleen Environmental Services — 207,083 — 207,083 Safety-Kleen Oil (2) — 99,464 — 99,464 Total third-party revenues $ 473,698 $ 306,547 $ 594 $ 780,839 For the Three Months Ended March 31, 2018 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 343,972 $ 287,642 $ 145 $ 631,759 Canada 95,716 22,276 27 118,019 Total third-party revenues $ 439,688 $ 309,918 $ 172 $ 749,778 Sources of Revenue (1) Technical Services $ 236,306 $ — $ — $ 236,306 Field and Emergency Response Services 69,935 — — 69,935 Industrial Services 103,763 — — 103,763 Oil, Gas and Lodging Services and Other 29,684 — 172 29,856 Safety-Kleen Environmental Services — 194,161 — 194,161 Safety-Kleen Oil (2) — 115,757 — 115,757 Total third-party revenues $ 439,688 $ 309,918 $ 172 $ 749,778 ______________________ (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) Safety-Kleen Oil was formerly known as Kleen Performance Products. 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 their 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 revenue is recognized and the deferred costs are expensed 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 emergencies include any scale from man-made disasters such as oil spills, to natural disasters such as hurricanes. These 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, days or even months for larger scale projects. Industrial Services. Industrial Services revenues are 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 directional boring services supporting drilling, completions and production programs. These 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. Oil, Gas and Lodging Services and Other. Oil, Gas and Lodging Services and Other is primarily comprised of revenues generated from providing Oil and Gas Field Services that support upstream activities such as exploration and drilling for oil and gas companies and Lodging Services to customers in Western Canada. The Company recognizes Oil and Gas Field Services revenue 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. Revenue for lodging accommodation services is recognized over time based on passage of time. 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, direct sales of blended oil products and other complementary services and product sales through a network of branch locations. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Other products and services include vacuum services, sale of complementary supply products including automotive fluids and shop supplies and other environmental services. Revenues from parts washer services include fees charged to customers for their use of parts washer equipment, to clean and maintain parts washer equipment and to remove and replace 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. Safety-Kleen Oil revenues are generated from sales of high-quality base and blended lubricating oils to third-party distributors, government agencies, fleets, railroads and industrial customers. The business also sells recycled fuel oil to asphalt plants, industrial plants, blenders, pulp and paper companies, vacuum gas oil producers and marine diesel oil producers. 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. Contract Balances March 31, 2019 December 31, 2018 Receivables $ 613,507 $ 606,952 Contract assets (unbilled receivables) 42,513 54,794 Contract liabilities (deferred revenue) 67,557 61,843 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 sheets. 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 sheets on a contract-by-contract basis at the end of each reporting period. As part of the acquisition of the Veolia Business (as defined in Note 4, "Business Combinations") on February 23, 2018, the Company acquired receivables and contract assets of $21.5 million and $18.1 million , respectively. Changes in the contract asset and liability balances during the three-month periods ended March 31, 2019 and December 31, 2018 were not materially impacted by any other factors. The contract liability balances at the beginning of each period presented were fully recognized in the subsequent three-month period. Variable Consideration The nature of the Company's contracts give rise to certain types of variable consideration, including in limited cases volume discounts. Accordingly, management establishes a revenue allowance to cover the estimated amounts of revenue that may need to be credited to customers' accounts in future periods. The Company estimates the amount of variable consideration to include in the estimated transaction price based on historical experience, anticipated performance and its best judgment at the time and to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Contract Costs Contract costs include direct and incremental costs to obtain or fulfill a contract. The Company’s contract costs that are subject to capitalization are comprised of costs associated with parts washer services and costs associated with the treatment and disposal of waste. Parts washer costs include costs of solvent, commissions paid relating to revenue generated from parts washer services and transportation costs associated with transferring the product picked up from the services as it is returned to the Company’s facilities or a third-party site. Costs related to the treatment of waste include costs for waste receiving, drum movement and storage, waste consolidation and transportation between facilities. Deferred costs associated with parts washer services are amortized ratably over the average service interval, which ranges between seven and 14 weeks. Deferred costs related to treatment and disposal of waste are recognized when the corresponding waste is disposed of and are included in deferred costs within total current assets in the Company’s Consolidated Balance Sheets. The deferred contract cost balances at the beginning of each period presented were fully recognized in cost of revenue in the subsequent three-month period.

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS 2019 Acquisition On March 1, 2019, the Company acquired certain assets of a privately-owned company for $10.4 million . The acquired assets complement 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 preliminary goodwill amount of $6.8 million was recognized. 2018 Acquisitions On August 31, 2018, the Company acquired a privately-owned company which expands the environmental services and waste oil capabilities of the Company for a $27.3 million purchase price, net of cash. The acquired company is included in the Safety-Kleen and Environmental Services segments. In connection with this acquisition, a preliminary goodwill amount of $12.4 million was recognized. The results of operations of this acquired business were not material in 2019. On February 23, 2018, the Company completed the acquisition of the U.S. Industrial Cleaning Business of Veolia Environmental Services North America LLC (the "Veolia Business"). The acquisition provides significant scale and industrial services capabilities while increasing the size of the Company's existing U.S. Industrial Services business. The Company acquired the Veolia Business for a purchase price of $124.5 million . The amount of pre-tax income for the three months ended March 31, 2018 was immaterial. During the three months ended March 31, 2019 , the Veolia Business was fully integrated into the Environmental Services segment, and therefore it is impracticable to measure earnings attributable to the Veolia Business for that period. The Company finalized purchase accounting for the Veolia Business in the first quarter of 2019. The components and allocation of the purchase price for the Veolia Business consist of the following amounts (in thousands): Final Allocation Accounts receivable, including unbilled receivables $ 39,558 Inventories and supplies 1,126 Prepaid expenses and other current assets 828 Property, plant and equipment 72,243 Permits and other intangibles 5,140 Current liabilities (18,372 ) Closure and post-closure liabilities (354 ) Total identifiable net assets 100,169 Goodwill 24,331 Total purchase price $ 124,500 The weighted average amortization period for the intangibles acquired is 8.2 years . The excess of the total purchase price, which includes the aggregate cash consideration paid in excess of the fair value of the tangible net assets and intangible assets acquired, was recorded as goodwill. The goodwill recognized is attributable to the expected operating synergies and growth potential that the Company expects to realize from this acquisition. Goodwill generated from the acquisition is deductible for tax purposes.

INVENTORIES AND SUPPLIES

INVENTORIES AND SUPPLIES	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
INVENTORIES AND SUPPLIES	INVENTORIES AND SUPPLIES Inventories and supplies consisted of the following (in thousands): March 31, 2019 December 31, 2018 Oil and oil products $ 67,888 $ 70,823 Supplies and drums 108,976 104,609 Solvent and solutions 10,500 10,657 Other 13,450 13,390 Total inventories and supplies $ 200,814 $ 199,479 Supplies and drums consist primarily of drums and containers used in providing the Company's products and services as well as critical spare parts to support the Company's incinerator and re-refinery operations. 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

PROPERTY, PLANT AND EQUIPMENT	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consisted of the following (in thousands): March 31, 2019 December 31, 2018 Land $ 129,684 $ 123,734 Asset retirement costs (non-landfill) 15,258 15,148 Landfill assets 160,093 154,918 Buildings and improvements (1) 465,707 440,188 Camp equipment 156,031 152,998 Vehicles 753,490 721,735 Equipment 1,711,470 1,697,490 Furniture and fixtures 5,476 5,453 Construction in progress 27,028 20,931 3,424,237 3,332,595 Less - accumulated depreciation and amortization 1,835,624 1,770,617 Total property, plant and equipment, net $ 1,588,613 $ 1,561,978 ______________________ (1) Inclusive of finance lease. Interest in the amount of $0.1 million and $0.3 million was capitalized to property, plant and equipment during the three months ended March 31, 2019 and March 31, 2018 , respectively. Depreciation expense, inclusive of landfill and finance lease amortization, was $65.9 million and $65.6 million for the three months ended March 31, 2019 and March 31, 2018 , respectively.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS The changes in goodwill by segment for the three months ended March 31, 2019 were as follows (in thousands): Environmental Services Safety-Kleen Totals Balance at January 1, 2019 $ 207,019 $ 307,170 $ 514,189 Increase from current period acquisitions — 6,825 6,825 Measurement period adjustments from prior period acquisitions (2,571 ) (1,422 ) (3,993 ) Foreign currency translation 412 477 889 Balance at March 31, 2019 $ 204,860 $ 313,050 $ 517,910 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 would more likely than not reduce the fair value of a reporting unit below its carrying value. As of March 31, 2019 and December 31, 2018 , the Company's total intangible assets consisted of the following (in thousands): March 31, 2019 December 31, 2018 Cost Accumulated Net Cost Accumulated Net Permits $ 180,463 $ 81,135 $ 99,328 $ 177,583 $ 79,358 $ 98,225 Customer and supplier relationships 397,949 187,195 210,754 393,487 179,824 213,663 Other intangible assets 37,616 31,363 6,253 37,262 29,743 7,519 Total amortizable permits and other intangible assets 616,028 299,693 316,335 608,332 288,925 319,407 Trademarks and trade names 122,623 — 122,623 122,468 — 122,468 Total permits and other intangible assets $ 738,651 $ 299,693 $ 438,958 $ 730,800 $ 288,925 $ 441,875 Amortization expense of permits and other intangible assets was $9.5 million and $9.2 million in the three months ended March 31, 2019 and March 31, 2018 , respectively. The expected amortization of the net carrying amount of finite-lived intangible assets at March 31, 2019 was as follows (in thousands): Years Ending December 31, Expected Amortization 2019 (nine months) $ 24,947 2020 31,289 2021 28,020 2022 27,849 2023 23,862 Thereafter 180,368 $ 316,335

ACCRUED EXPENSES

ACCRUED EXPENSES	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
ACCRUED EXPENSES	ACCRUED EXPENSES Accrued expenses consisted of the following at March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Insurance $ 64,298 $ 70,217 Interest 14,783 3,930 Accrued compensation and benefits 46,757 77,881 Income, real estate, sales and other taxes 30,289 25,670 Other 52,259 55,707 $ 208,386 $ 233,405

CLOSURE AND POST-CLOSURE LIABIL

CLOSURE AND POST-CLOSURE LIABILITIES	3 Months Ended
	Mar. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
CLOSURE AND POST-CLOSURE LIABILITIES	CLOSURE AND POST-CLOSURE LIABILITIES The changes to closure and post-closure liabilities (also referred to as “asset retirement obligations”) from January 1, 2019 through March 31, 2019 were as follows (in thousands): Landfill Non-Landfill Total Balance at January 1, 2019 $ 37,809 $ 32,122 $ 69,931 Liabilities assumed in acquisition — 98 98 New asset retirement obligations 719 — 719 Accretion 742 689 1,431 Changes in estimates recorded to statement of operations — 40 40 Changes in estimates recorded to balance sheet 2,798 — 2,798 Expenditures (163 ) (629 ) (792 ) Currency translation and other 50 146 196 Balance at March 31, 2019 $ 41,955 $ 32,466 $ 74,421 All the landfill facilities included in the above were active as of March 31, 2019 . There were no significant charges (benefits) in 2019 resulting from changes in estimates for closure and post-closure liabilities. New asset retirement obligations incurred during the first three months of 2019 were discounted at the credit-adjusted risk-free rate of 6.02% .

REMEDIAL LIABILITIES

REMEDIAL LIABILITIES	3 Months Ended
	Mar. 31, 2019
Environmental Remediation Obligations [Abstract]
REMEDIAL LIABILITIES	REMEDIAL LIABILITIES The changes to remedial liabilities for the three months ended March 31, 2019 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, 2019 $ 1,838 $ 65,315 $ 53,864 $ 121,017 Accretion 22 675 446 1,143 Changes in estimates recorded to statement of operations 23 172 (1,009 ) (814 ) Expenditures (15 ) (1,154 ) (1,303 ) (2,472 ) Currency translation and other — 10 77 87 Balance at March 31, 2019 $ 1,868 $ 65,018 $ 52,075 $ 118,961 In the three months ended March 31, 2019 , there were no significant charges (benefits) resulting from changes in estimates for remedial liabilities.

FINANCING ARRANGEMENTS

FINANCING ARRANGEMENTS	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
FINANCING ARRANGEMENTS	FINANCING ARRANGEMENTS The following table is a summary of the Company’s financing arrangements (in thousands): Current Obligations: March 31, 2019 December 31, 2018 Senior secured Term Loan Agreement ("Term Loan Agreement") $ 7,535 $ 7,535 Long-Term Obligations: Senior secured Term Loan Agreement due June 30, 2024 $ 732,813 $ 734,697 Senior unsecured notes, at 5.125%, due June 1, 2021 ("2021 Notes") 845,000 845,000 Long-term obligations, at par $ 1,577,813 $ 1,579,697 Unamortized debt issuance costs and premium, net (13,808 ) (14,676 ) Long-term obligations, at carrying value $ 1,564,005 $ 1,565,021 Financing Activities At March 31, 2019 and December 31, 2018 , the fair value of the Term Loan Agreement debt was $738.5 million and $707.0 million , respectively, based on quoted market prices or other available market data. At March 31, 2019 and December 31, 2018 , the fair value of the Company's 2021 Notes was $846.1 million and $845.0 million , respectively, based on quoted market prices for the instrument. The fair values of the Company's currently outstanding term loans under the Term Loan Agreement (the "Term Loans") and 2021 Notes are considered Level 2 measures according to the fair value hierarchy. The Company also maintains a $400.0 million revolving credit facility under which the Company had no outstanding loan balance as of March 31, 2019 and December 31, 2018 . At March 31, 2019 , approximately $209.1 million was available to borrow and outstanding letters of credit were $153.3 million . At December 31, 2018 , $235.4 million was available to borrow and outstanding letters of credit were $130.1 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 all $740.3 million aggregate principal amount of Term Loans which were outstanding on March 31, 2019 is variable under the Term Loan Agreement, 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 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 rate of approximately 2.92% . When combined with the 1.75% interest rate margin for Eurocurrency borrowings, the effective annual interest rate on such $350.0 million aggregate principal amount of Term Loans is therefore approximately 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 March 31, 2019 and December 31, 2018 , the Company has recorded a derivative liability with a fair value of $13.4 million and $8.8 million , respectively, within accrued expenses in connection with these cash flow hedges. The fair value of the interest rate swaps included in the Level 2 tier of the fair value hierarchy 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 swaps. 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.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2019
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 months ended March 31, 2019 was 86.0% compared to (31.9)% for the same period in 2018 . The variations in the effective income tax rates for the three months ended March 31, 2019 and March 31, 2018 , as compared to more customary relationships between pre-tax income and the provision for income taxes, were primarily due to not recognizing income tax benefits from current operating losses related to certain Canadian entities during these periods. As of March 31, 2019 and December 31, 2018 , the Company had recorded $3.2 million of liabilities for unrecognized tax benefits and $0.8 million of interest. During the first quarter of 2019 the Company was notified by the Internal Revenue Service (“IRS”) of their intent to examine tax years 2014-2016. The Company does not believe the examination will result in material liabilities. Due to expiring statute of limitation periods, the Company believes that total unrecognized tax benefits will decrease by $0.6 million within the next 12 months.

EARNINGS (LOSS) PER SHARE

EARNINGS (LOSS) PER SHARE	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
EARNINGS (LOSS) PER SHARE	EARNINGS (LOSS) PER SHARE The following are computations of basic and diluted earnings (loss) per share (in thousands except for per share amounts): Three Months Ended March 31, 2019 2018 Numerator for basic and diluted earnings (loss) per share: Net income (loss) $ 976 $ (12,631 ) Denominator: Basic shares outstanding 55,848 56,457 Dilutive effect of stock-based compensation awards 234 — Dilutive shares outstanding 56,082 56,457 Basic income (loss) per share: $ 0.02 $ (0.22 ) Diluted income (loss) per share: $ 0.02 $ (0.22 ) For the three months ended March 31, 2019 , the dilutive effect of all then outstanding restricted stock and performance awards is included in the earnings per share calculation above except for 78,271 of performance stock awards for which the performance criteria were not attained at that time and 27,357 of restricted stock awards which were antidilutive. As a result of the net loss reported for the three months ended March 31, 2018 , all then outstanding restricted stock awards and performance awards totaling 896,180 were excluded from the calculation of diluted loss per share as their inclusion would have an antidilutive effect.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	ACCUMULATED OTHER COMPREHENSIVE LOSS The changes in accumulated other comprehensive loss by component and related tax effects for the three months ended March 31, 2019 were as follows (in thousands): Foreign Currency Translation Unrealized Losses (Gains) on Available-For-Sale Securities Unrealized Losses on Interest Rate Hedge Unfunded Pension Liability Total Balance at January 1, 2019 $ (212,925 ) $ (69 ) $ (8,773 ) $ (1,604 ) $ (223,371 ) Other comprehensive income (loss) before tax effects 8,540 174 (5,017 ) — 3,697 Tax impact related to items in other comprehensive income (loss) — (31 ) — — (31 ) Amounts reclassified out of accumulated other comprehensive loss — — 358 — 358 Other comprehensive income (loss) 8,540 143 (4,659 ) — 4,024 Balance at March 31, 2019 $ (204,385 ) $ 74 $ (13,432 ) $ (1,604 ) $ (219,347 ) The amounts reclassified out of accumulated other comprehensive loss into the consolidated statement of operations, with presentation location, during the three months ended March 31, 2019 were as follows (in thousands): For the Three Months Ended March 31, 2019 Other Comprehensive Income (Loss) Components Location Unrealized loss on interest rate hedge $ (358 ) Interest expense, net of interest income There were no reclassifications out of accumulated other comprehensive loss during the three months ended March 31, 2018 .

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Total stock-based compensation cost charged to selling, general and administrative expenses for the three months ended March 31, 2019 and March 31, 2018 was $5.8 million and $3.1 million , respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation was $1.1 million and $0.9 million for the three months ended March 31, 2019 and March 31, 2018 , respectively. Restricted Stock Awards The following information relates to restricted stock awards that have been granted to employees and directors under the Company's equity incentive plan adopted in 2010 (the "2010 Plan"). The restricted stock awards are not transferable until vested and the restrictions generally lapse upon the achievement of continued employment over a three -to- five -year period or service as a director until the following annual meeting of shareholders. The fair value of each restricted stock grant is based on the closing price of the Company's common stock on the date of grant and is amortized to expense over its vesting period. The following table summarizes information about restricted stock awards for the three months ended March 31, 2019 : Restricted Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2019 657,240 $ 54.65 Granted 42,300 61.18 Vested (61,391 ) 52.83 Forfeited (21,870 ) 54.39 Balance at March 31, 2019 616,279 54.51 As of March 31, 2019 , there was $23.1 million of total unrecognized compensation cost arising from restricted stock awards under the Company's 2010 Plan. This cost is expected to be recognized over a weighted average period of 2.6 years. The total fair value of restricted stock vested during the three months ended March 31, 2019 and March 31, 2018 was $3.2 million and $1.3 million , respectively. Performance Stock Awards The following information relates to performance stock awards that have been granted to employees under the Company's 2010 Plan. 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 such 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 fair value of each performance stock award is based on the closing price of the Company's common stock on the date of grant and is amortized to expense over the service period if achievement of performance measures is considered probable. The following table summarizes information about performance stock awards for the three months ended March 31, 2019 : Performance Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2019 213,490 $ 55.71 Granted — — Vested (51,996 ) 55.77 Forfeited (14,120 ) 55.69 Balance at March 31, 2019 147,374 55.69 As of March 31, 2019 , there was $4.6 million of total unrecognized compensation cost arising from unvested performance stock awards deemed probable of vesting under the Company's 2010 Plan. The total fair value of performance awards vested during the three months ended March 31, 2019 and March 31, 2018 was $2.9 million and $0.5 million , respectively . Common Stock Repurchases The Company's board of directors has authorized the repurchase of up to $600 million of the Company's common stock. During the three months ended March 31, 2019 and March 31, 2018 , the Company repurchased and retired a total of approximately 0.1 million and 0.3 million shares, respectively, of the Company's common stock for total costs of approximately $6.3 million and $14.3 million , respectively. Through March 31, 2019 , the Company has repurchased and retired a total of approximately 5.7 million shares of its common stock for approximately $300.3 million under this program. As of March 31, 2019 , an additional $299.7 million remained available for repurchase of shares under this program.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2019
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 wastes. At March 31, 2019 and December 31, 2018 , the Company had recorded reserves of $23.8 million and $25.4 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. At March 31, 2019 and December 31, 2018 , the Company also believed that it was reasonably possible that the amount of these potential liabilities could be as much as $1.8 million more. 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 March 31, 2019 and December 31, 2018 , the $23.8 million and $25.4 million , respectively, of reserves consisted of (i) $17.6 million and $17.9 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) $6.2 million and $7.5 million , respectively, primarily related to federal, state and provincial enforcement actions, which were included in accrued expenses on the consolidated balance sheets. As of March 31, 2019 , the principal legal and administrative proceedings in which the Company was involved, or which had been terminated during 2019 , 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 March 31, 2019 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 March 31, 2019 , wherein persons claim personal injury resulting from the use of Safety-Kleen's parts cleaning equipment or cleaning products. These proceedings typically involve allegations that the solvent used in Safety-Kleen's parts cleaning 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. Safety-Kleen 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. Safety-Kleen 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, Safety-Kleen is unable to ascertain the ultimate aggregate amount of monetary liability or financial impact with respect to these matters as of March 31, 2019 . From January 1, 2019 to March 31, 2019 , seven 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 Safety-Kleen's 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 128 sites which are subject to or are proposed to become subject to proceedings under federal or state Superfund laws. Of the 128 sites, five (including the BR Facility described below) involve facilities that are now owned or leased by the Company and 123 involve third-party sites to which either the Company or the prior owners of certain of the Company’s facilities shipped wastes. Of the 123 third-party sites, 30 are now settled, 16 are currently requiring expenditures on remediation and 77 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 ten of the 123 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 ("the 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 123 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 123 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 March 31, 2019 and December 31, 2018 , there were 11 and ten 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.

LEASES

LEASES	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
LEASES	LEASES As of March 31, 2019 , the Company’s leases were all operating leases except for a single finance lease related to the Company’s corporate headquarters, which was amended during the first quarter of 2019, resulting in the classification as a finance lease. The Company’s lease expense was as follows (in thousands): For the Three Months Ended March 31, 2019 Operating lease cost $ 13,362 Finance lease cost Amortization of ROU asset 245 Interest on lease liability 321 Total finance lease cost 566 Short-term lease cost 19,714 Variable lease cost 1,242 Total lease cost $ 34,884 Other information related to leases was as follows (in thousands, except lease term and discount rate): Supplemental Lease Balance Sheet Information: March 31, 2019 ROU assets Operating leases $ 170,550 Finance lease (included in property, plant and equipment, net) 22,782 Current portion of lease liabilities Operating leases 43,858 Finance lease (included in accrued expenses) 413 Long-term portion of lease liabilities Operating leases 128,689 Finance lease (included in deferred taxes, unrecognized tax benefits and other long-term liabilities) 23,797 Weighted Average Remaining Lease Term (years) March 31, 2019 Operating leases 5.3 Finance lease 23.3 Weighted Average Discount Rate Operating leases 5.42 % Finance lease 5.25 % At March 31, 2019 , our future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands): Years Ending December 31, Operating Leases Finance Lease 2019 (nine months) $ 40,019 $ 1,307 2020 44,558 1,777 2021 33,147 1,813 2022 26,081 1,849 2023 18,498 1,886 2024 12,525 1,923 Thereafter 26,037 40,636 Total future lease payments 200,865 51,191 Amount representing interest (28,318 ) (26,981 ) Total lease liabilities $ 172,547 $ 24,210 At March 31, 2019 , none of our executed leases that had not yet commenced will create significant rights or obligations in the future and our sublease transactions are not material. Additionally, the Company does not have any related party leases and there were no restrictions or covenants imposed by its leases. Disclosures related to periods prior to adoption of Topic 842 The following is a summary of future minimum payments under operating leases that have initial or remaining non-cancelable lease terms in excess of one year at December 31, 2018 (in thousands): Year Total Operating Leases 2019 $ 56,480 2020 45,467 2021 33,564 2022 24,509 2023 15,253 Thereafter 35,778 Total minimum lease payments $ 211,051 During the years ended December 31, 2018, 2017 and 2016, rent expense including short-term rentals was approximately $141.1 million , $125.4 million , and $121.9 million , respectively.

SEGMENT REPORTING

SEGMENT REPORTING	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
SEGMENT REPORTING	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's operations are managed in two operating segments: Environmental Services and Safety-Kleen. Third-party revenue is revenue billed to outside customers by a particular segment. Direct revenue 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 months ended March 31, 2019 and March 31, 2018 (in thousands): For the Three Months Ended March 31, 2019 For the Three Months Ended March 31, 2018 Third-party revenues Intersegment revenues, net Corporate Items, net Direct revenues Third-party revenues Intersegment revenues, net Corporate Items, net Direct revenues Environmental Services $ 473,698 $ 34,075 $ 1,249 $ 509,022 $ 439,688 $ 31,965 $ 794 $ 472,447 Safety-Kleen 306,547 (34,075 ) 5 272,477 309,918 (31,965 ) 11 277,964 Corporate Items 594 — (1,254 ) (660 ) 172 — (805 ) (633 ) Total $ 780,839 $ — $ — $ 780,839 $ 749,778 $ — $ — $ 749,778 The primary financial measure by which the Company evaluates the performance of its segments is "Adjusted EBITDA," which consists of net income (loss) plus accretion of environmental liabilities, depreciation and amortization, interest expense, net of interest income, provision for income taxes and other gains or non-cash charges not deemed representative of fundamental segment results and excludes other (income) expense, 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 March 31, 2019 2018 Adjusted EBITDA: Environmental Services $ 89,510 $ 61,417 Safety-Kleen 54,793 61,884 Corporate Items (42,640 ) (35,036 ) Total 101,663 88,265 Reconciliation to Consolidated Statements of Operations: Accretion of environmental liabilities 2,574 2,430 Depreciation and amortization 75,355 74,844 Income from operations 23,734 10,991 Other (income) expense, net (2,983 ) 299 Interest expense, net of interest income 19,764 20,270 Income (loss) before provision for income taxes $ 6,953 $ (9,578 ) The following table presents certain assets by reportable segment and in the aggregate (in thousands): March 31, 2019 December 31, 2018 Property, plant and equipment, net Environmental Services $ 953,960 $ 951,867 Safety-Kleen 561,041 553,220 Corporate Items 73,612 56,891 Total property, plant and equipment, net $ 1,588,613 $ 1,561,978 Goodwill and Permits and other intangibles, net Environmental Services Goodwill $ 204,860 $ 207,019 Permits and other intangibles, net 95,040 93,313 Total Environmental Services 299,900 300,332 Safety-Kleen Goodwill $ 313,050 $ 307,170 Permits and other intangibles, net 343,918 348,562 Total Safety-Kleen 656,968 655,732 Total $ 956,868 $ 956,064 The following table presents the total assets by reportable segment (in thousands): March 31, 2019 December 31, 2018 Environmental Services $ 1,724,208 $ 1,640,706 Safety-Kleen 1,518,723 1,431,381 Corporate Items 639,123 666,234 Total $ 3,882,054 $ 3,738,321 The following table presents the total assets by geographical area (in thousands): March 31, 2019 December 31, 2018 United States $ 3,212,979 $ 3,090,311 Canada 669,075 648,010 Total $ 3,882,054 $ 3,738,321

GUARANTOR AND NON-GUARANTOR SUB

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION	3 Months Ended
	Mar. 31, 2019
Guarantor and Non-Guarantor Subsidiaries Financial Information [Abstract]
GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION	GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION The 2021 Notes and the Company's obligations under its Term Loan Agreement are guaranteed by substantially all of the Company’s subsidiaries organized in the United States. Each guarantor is a 100% owned subsidiary of Clean Harbors, Inc. and its guarantee is both full and unconditional and joint and several. The guarantees are, however, subject to customary release provisions under which the guarantee of any domestic restricted subsidiary will be released if the Company sells such subsidiary to an unrelated third party in accordance with the terms of the indentures which govern the 2021 Notes and of the Term Loan Agreement. The 2021 Notes and the Company's obligations under its Term Loan Agreement are not guaranteed by the Company’s subsidiaries organized outside the United States. The following supplemental condensed consolidating financial information for the parent company, the guarantor subsidiaries and the non-guarantor subsidiaries, respectively, is presented in conformity with the requirements of Rule 3-10 of SEC Regulation S-X (“Rule 3-10”). Following is the condensed consolidating balance sheet at March 31, 2019 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 27,431 $ 75,099 $ 64,841 $ — $ 167,371 Short-term marketable securities 121 — 57,356 — 57,477 Intercompany receivables 268,195 701,583 58,138 (1,027,916 ) — Accounts receivable, net — 526,047 87,460 — 613,507 Other current assets — 281,802 44,525 (16,560 ) 309,767 Property, plant and equipment, net — 1,261,206 327,407 — 1,588,613 Investments in subsidiaries 3,176,613 566,296 — (3,742,909 ) — Intercompany debt receivable — 14,900 21,000 (35,900 ) — Operating lease right-of-use assets — 137,591 32,959 — 170,550 Goodwill — 459,139 58,771 — 517,910 Permits and other intangibles, net — 390,838 48,120 — 438,958 Other long-term assets 1,437 13,530 2,903 31 17,901 Total assets $ 3,473,797 $ 4,428,031 $ 803,480 $ (4,823,254 ) $ 3,882,054 Liabilities and Stockholders’ Equity: Current liabilities $ 35,686 $ 431,891 $ 146,493 $ (16,560 ) $ 597,510 Intercompany payables 702,141 325,025 750 (1,027,916 ) — Closure, post-closure and remedial liabilities, net — 147,944 17,524 — 165,468 Long-term obligations, net 1,564,005 — — — 1,564,005 Operating lease liabilities, less current portion — 104,374 24,315 — 128,689 Intercompany debt payable — 21,000 14,900 (35,900 ) — Other long-term liabilities — 233,979 20,407 31 254,417 Total liabilities 2,301,832 1,264,213 224,389 (1,080,345 ) 2,710,089 Stockholders’ equity 1,171,965 3,163,818 579,091 (3,742,909 ) 1,171,965 Total liabilities and stockholders’ equity $ 3,473,797 $ 4,428,031 $ 803,480 $ (4,823,254 ) $ 3,882,054 Following is the condensed consolidating balance sheet at December 31, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 27,308 $ 101,302 $ 97,897 $ — $ 226,507 Short-term marketable securities 67 — 52,789 — 52,856 Intercompany receivables 262,475 721,521 60,693 (1,044,689 ) — Accounts receivable, net — 520,785 86,167 — 606,952 Other current assets — 289,869 49,631 (23,657 ) 315,843 Property, plant and equipment, net — 1,233,578 328,400 — 1,561,978 Investments in subsidiaries 3,162,704 571,304 — (3,734,008 ) — Intercompany debt receivable — 14,669 21,000 (35,669 ) — Goodwill — 456,307 57,882 — 514,189 Permits and other intangibles, net — 393,045 48,830 — 441,875 Other long-term assets 1,551 13,545 3,025 — 18,121 Total assets $ 3,454,105 $ 4,315,925 $ 806,314 $ (4,838,023 ) $ 3,738,321 Liabilities and Stockholders’ Equity: Current liabilities $ 20,170 $ 457,164 $ 148,601 $ (23,657 ) $ 602,278 Intercompany payables 699,158 321,846 23,685 (1,044,689 ) — Closure, post-closure and remedial liabilities, net — 151,480 16,434 — 167,914 Long-term obligations, net 1,565,021 — — — 1,565,021 Intercompany debt payable — 21,000 14,669 (35,669 ) — Other long-term liabilities — 212,924 20,428 — 233,352 Total liabilities 2,284,349 1,164,414 223,817 (1,104,015 ) 2,568,565 Stockholders’ equity 1,169,756 3,151,511 582,497 (3,734,008 ) 1,169,756 Total liabilities and stockholders’ equity $ 3,454,105 $ 4,315,925 $ 806,314 $ (4,838,023 ) $ 3,738,321 Following is the consolidating statement of operations for the three months ended March 31, 2019 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 529,656 $ 144,139 $ (17,137 ) $ 656,658 Product revenues — 115,038 12,384 (3,241 ) 124,181 Total revenues — 644,694 156,523 (20,378 ) 780,839 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 356,590 124,030 (17,137 ) 463,483 Product cost of revenues — 99,357 4,765 (3,241 ) 100,881 Total cost of revenues — 455,947 128,795 (20,378 ) 564,364 Selling, general and administrative expenses 57 93,526 21,229 — 114,812 Accretion of environmental liabilities — 2,267 307 — 2,574 Depreciation and amortization — 57,335 18,020 — 75,355 (Loss) income from operations (57 ) 35,619 (11,828 ) — 23,734 Other income (expense), net 50 2,962 (29 ) — 2,983 Interest (expense) income, net (20,374 ) 9 601 — (19,764 ) Equity in earnings of subsidiaries, net of taxes 15,636 (13,336 ) — (2,300 ) — Intercompany interest income (expense) — 197 (197 ) — — (Loss) income before (benefit) provision for income taxes (4,745 ) 25,451 (11,453 ) (2,300 ) 6,953 (Benefit) provision for income taxes (5,721 ) 11,418 280 — 5,977 Net income (loss) 976 14,033 (11,733 ) (2,300 ) 976 Other comprehensive income 4,024 4,024 8,328 (12,352 ) 4,024 Comprehensive income (loss) $ 5,000 $ 18,057 $ (3,405 ) $ (14,652 ) $ 5,000 Following is the consolidating statement of operations for the three months ended March 31, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 481,483 $ 152,401 $ (14,165 ) $ 619,719 Product revenues — 121,582 11,450 (2,973 ) 130,059 Total revenues — 603,065 163,851 (17,138 ) 749,778 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 328,180 133,634 (14,165 ) 447,649 Product cost of revenues — 95,038 6,711 (2,973 ) 98,776 Total cost of revenues — 423,218 140,345 (17,138 ) 546,425 Selling, general and administrative expenses 35 93,843 21,210 — 115,088 Accretion of environmental liabilities — 2,176 254 — 2,430 Depreciation and amortization — 53,704 21,140 — 74,844 (Loss) income from operations (35 ) 30,124 (19,098 ) — 10,991 Other expense, net — (85 ) (214 ) — (299 ) Interest (expense) income, net (20,999 ) 505 224 — (20,270 ) Equity in earnings of subsidiaries, net of taxes 2,514 (20,062 ) — 17,548 — Intercompany interest income (expense) — 1,361 (1,361 ) — — (Loss) income before (benefit) provision for income taxes (18,520 ) 11,843 (20,449 ) 17,548 (9,578 ) (Benefit) provision for income taxes (5,889 ) 9,101 (159 ) — 3,053 Net (loss) income (12,631 ) 2,742 (20,290 ) 17,548 (12,631 ) Other comprehensive loss (16,746 ) (16,746 ) (14,007 ) 30,753 (16,746 ) Comprehensive loss $ (29,377 ) $ (14,004 ) $ (34,297 ) $ 48,301 $ (29,377 ) Following is the condensed consolidating statement of cash flows for the three months ended March 31, 2019 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash from operating activities $ 123 $ 50,344 $ (20,727 ) $ — $ 29,740 Cash flows used in investing activities: Additions to property, plant and equipment — (48,696 ) (10,251 ) — (58,947 ) Proceeds from sale and disposal of fixed assets — 3,366 955 — 4,321 Acquisitions, net of cash acquired — (14,870 ) — — (14,870 ) Additions to intangible assets including costs to obtain or renew permits — (1,294 ) 162 — (1,132 ) Proceeds from sale of available-for-sale securities — — 8,600 — 8,600 Purchases of available-for-sale securities — — (12,941 ) — (12,941 ) Intercompany — (10,484 ) — 10,484 — Net cash used in investing activities — (71,978 ) (13,475 ) 10,484 (74,969 ) Cash flows used in financing activities: Change in uncashed checks — (4,454 ) (315 ) — (4,769 ) Tax payments related to withholdings on vested restricted stock (2,276 ) — — — (2,276 ) Repurchases of common stock (6,324 ) — — — (6,324 ) Payments on finance lease — (115 ) — — (115 ) Principal payment on debt (1,884 ) — — — (1,884 ) Intercompany 10,484 — — (10,484 ) — Net cash used in financing activities — (4,569 ) (315 ) (10,484 ) (15,368 ) Effect of exchange rate change on cash — — 1,461 — 1,461 Increase (decrease) in cash and cash equivalents 123 (26,203 ) (33,056 ) — (59,136 ) Cash and cash equivalents, beginning of period 27,308 101,302 97,897 — 226,507 Cash and cash equivalents, end of period $ 27,431 $ 75,099 $ 64,841 $ — $ 167,371 Following is the condensed consolidating statement of cash flows for the three months ended March 31, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash from (used in) operating activities $ 143 $ 69,536 $ (17,776 ) $ — $ 51,903 Cash flows used in investing activities: Additions to property, plant and equipment — (37,319 ) (6,923 ) — (44,242 ) Proceeds from sale and disposal of fixed assets — 292 506 — 798 Acquisitions, net of cash acquired — (120,000 ) — — (120,000 ) Additions to intangible assets including costs to obtain or renew permits — (1,234 ) (11 ) — (1,245 ) Proceeds from sale of available-for-sale securities — — 3,264 — 3,264 Purchases of available-for-sale securities — — (3,003 ) — (3,003 ) Intercompany — (15,812 ) — 15,812 — Net cash used in investing activities — (174,073 ) (6,167 ) 15,812 (164,428 ) Cash flows used in financing activities: Change in uncashed checks — (3,578 ) (265 ) — (3,843 ) Tax payments related to withholdings on vested restricted stock (548 ) — — — (548 ) Repurchases of common stock (14,264 ) — — — (14,264 ) Principal payment on debt (1,000 ) — — — (1,000 ) Intercompany 15,812 — — (15,812 ) — Net cash used in financing activities — (3,578 ) (265 ) (15,812 ) (19,655 ) Effect of exchange rate change on cash — — (867 ) — (867 ) Increase (decrease) in cash and cash equivalents 143 (108,115 ) (25,075 ) — (133,047 ) Cash and cash equivalents, beginning of period 51,638 207,777 59,984 — 319,399 Cash and cash equivalents, end of period $ 51,781 $ 99,662 $ 34,909 $ — $ 186,352

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Standards implemented In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842) . The amendment increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The Company adopted Topic 842 on January 1, 2019 using the modified retrospective method of adoption. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company's historical accounting methodology pursuant to ASC 840, Leases . As permitted under the transition guidance, the Company elected to apply the package of three practical expedients for all existing leases which, among other things, allowed us to maintain the lease classification for all existing leases at the adoption date. The adoption of Topic 842 resulted in the recognition of right-of-use (“ROU”) assets of $185.5 million and total current and noncurrent lease liabilities of $188.5 million at adoption. Additionally, Topic 842 required new and expanded disclosures to enable users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The standard did not have a material impact on the consolidated statements of operations or cash flows. Leases The Company’s leases predominately relate to real estate and equipment such as vehicles and industrial equipment utilized in operations as well as rail cars utilized in connection with the Company’s transportation needs. Contracts are reviewed at inception to determine if the arrangement is a lease and, if so, whether it is an operating or finance lease. For all of its leases, the Company has elected not to separate lease and nonlease components, such as common area maintenance. The Company generally enters into real estate leases with five to ten-year terms and non-real estate leases with two to seven-year terms. In the normal course of business, the Company also enters into short-term leases having terms of less than one-year. These leases are generally equipment leases entered into for short periods of time (e.g. daily, weekly or monthly), and done so to satisfy immediate and/or short-term operational needs of the business which can arise based upon the nature of particular services performed or seasonality factors. The Company has elected not to recognize ROU assets and lease liabilities for these short-term leases. Expense for all such short-term leases is disclosed as short-term lease cost as shown in Note 17, "Leases." Operating and finance leases with terms exceeding one year are recognized as ROU assets and lease liabilities and measured based on the present value of the future lease payments over the lease term at commencement date. When applicable, the ROU asset includes any lease payments made at or before the commencement date and initial direct costs incurred and is reduced by lease incentives received under the lease agreement, if any. Certain of the Company's real estate leases contain escalating future lease payments. Escalating lease payments that are based upon explicit amounts contained in the lease or an index (e.g., consumer price index) are included in its determination of future lease payments to determine the ROU asset and lease liability recognized at the commencement date. Any differences in the future lease payments from initial recognition are not anticipated to be material and will be recorded as variable lease cost in the period incurred. The variable lease cost will also include the Company’s portion of property tax, utilities and common area maintenance. A significant portion of the Company’s real estate lease agreements include renewal periods at the Company’s option. The Company includes these renewal periods in the lease term only when renewal is reasonably certain based upon facts and circumstances specific to the lease and known by the Company. The Company uses its incremental borrowing rate on collateralized debt based on the information available at the lease commencement date in determining the present value of future lease payments as the implicit rate is typically not readily determinable.

REVENUES (Tables)

REVENUES (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents the Company’s third-party revenues disaggregated by revenue source (in thousands): For the Three Months Ended March 31, 2019 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 388,169 $ 286,574 $ 594 $ 675,337 Canada 85,529 19,973 — 105,502 Total third-party revenues $ 473,698 $ 306,547 $ 594 $ 780,839 Sources of Revenue (1) Technical Services $ 251,919 $ — $ — $ 251,919 Field and Emergency Response Services 71,626 — — 71,626 Industrial Services 116,098 — — 116,098 Oil, Gas and Lodging Services and Other 34,055 — 594 34,649 Safety-Kleen Environmental Services — 207,083 — 207,083 Safety-Kleen Oil (2) — 99,464 — 99,464 Total third-party revenues $ 473,698 $ 306,547 $ 594 $ 780,839 For the Three Months Ended March 31, 2018 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 343,972 $ 287,642 $ 145 $ 631,759 Canada 95,716 22,276 27 118,019 Total third-party revenues $ 439,688 $ 309,918 $ 172 $ 749,778 Sources of Revenue (1) Technical Services $ 236,306 $ — $ — $ 236,306 Field and Emergency Response Services 69,935 — — 69,935 Industrial Services 103,763 — — 103,763 Oil, Gas and Lodging Services and Other 29,684 — 172 29,856 Safety-Kleen Environmental Services — 194,161 — 194,161 Safety-Kleen Oil (2) — 115,757 — 115,757 Total third-party revenues $ 439,688 $ 309,918 $ 172 $ 749,778 ______________________ (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) Safety-Kleen Oil was formerly known as Kleen Performance Products.
Contract Balances	ontract Balances March 31, 2019 December 31, 2018 Receivables $ 613,507 $ 606,952 Contract assets (unbilled receivables) 42,513 54,794 Contract liabilities (deferred revenue) 67,557 61,843

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	The components and allocation of the purchase price for the Veolia Business consist of the following amounts (in thousands): Final Allocation Accounts receivable, including unbilled receivables $ 39,558 Inventories and supplies 1,126 Prepaid expenses and other current assets 828 Property, plant and equipment 72,243 Permits and other intangibles 5,140 Current liabilities (18,372 ) Closure and post-closure liabilities (354 ) Total identifiable net assets 100,169 Goodwill 24,331 Total purchase price $ 124,500

INVENTORIES AND SUPPLIES (Table

INVENTORIES AND SUPPLIES (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventories and supplies consisted of the following (in thousands): March 31, 2019 December 31, 2018 Oil and oil products $ 67,888 $ 70,823 Supplies and drums 108,976 104,609 Solvent and solutions 10,500 10,657 Other 13,450 13,390 Total inventories and supplies $ 200,814 $ 199,479

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment consisted of the following (in thousands): March 31, 2019 December 31, 2018 Land $ 129,684 $ 123,734 Asset retirement costs (non-landfill) 15,258 15,148 Landfill assets 160,093 154,918 Buildings and improvements (1) 465,707 440,188 Camp equipment 156,031 152,998 Vehicles 753,490 721,735 Equipment 1,711,470 1,697,490 Furniture and fixtures 5,476 5,453 Construction in progress 27,028 20,931 3,424,237 3,332,595 Less - accumulated depreciation and amortization 1,835,624 1,770,617 Total property, plant and equipment, net $ 1,588,613 $ 1,561,978 ______________________ (1) Inclusive of finance lease.

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes to goodwill	The changes in goodwill by segment for the three months ended March 31, 2019 were as follows (in thousands): Environmental Services Safety-Kleen Totals Balance at January 1, 2019 $ 207,019 $ 307,170 $ 514,189 Increase from current period acquisitions — 6,825 6,825 Measurement period adjustments from prior period acquisitions (2,571 ) (1,422 ) (3,993 ) Foreign currency translation 412 477 889 Balance at March 31, 2019 $ 204,860 $ 313,050 $ 517,910
Summary of indefinite-lived intangible assets	As of March 31, 2019 and December 31, 2018 , the Company's total intangible assets consisted of the following (in thousands): March 31, 2019 December 31, 2018 Cost Accumulated Net Cost Accumulated Net Permits $ 180,463 $ 81,135 $ 99,328 $ 177,583 $ 79,358 $ 98,225 Customer and supplier relationships 397,949 187,195 210,754 393,487 179,824 213,663 Other intangible assets 37,616 31,363 6,253 37,262 29,743 7,519 Total amortizable permits and other intangible assets 616,028 299,693 316,335 608,332 288,925 319,407 Trademarks and trade names 122,623 — 122,623 122,468 — 122,468 Total permits and other intangible assets $ 738,651 $ 299,693 $ 438,958 $ 730,800 $ 288,925 $ 441,875
Schedule of finite-lived intangible assets	As of March 31, 2019 and December 31, 2018 , the Company's total intangible assets consisted of the following (in thousands): March 31, 2019 December 31, 2018 Cost Accumulated Net Cost Accumulated Net Permits $ 180,463 $ 81,135 $ 99,328 $ 177,583 $ 79,358 $ 98,225 Customer and supplier relationships 397,949 187,195 210,754 393,487 179,824 213,663 Other intangible assets 37,616 31,363 6,253 37,262 29,743 7,519 Total amortizable permits and other intangible assets 616,028 299,693 316,335 608,332 288,925 319,407 Trademarks and trade names 122,623 — 122,623 122,468 — 122,468 Total permits and other intangible assets $ 738,651 $ 299,693 $ 438,958 $ 730,800 $ 288,925 $ 441,875
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 March 31, 2019 was as follows (in thousands): Years Ending December 31, Expected Amortization 2019 (nine months) $ 24,947 2020 31,289 2021 28,020 2022 27,849 2023 23,862 Thereafter 180,368 $ 316,335

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Accrued expenses	Accrued expenses consisted of the following at March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Insurance $ 64,298 $ 70,217 Interest 14,783 3,930 Accrued compensation and benefits 46,757 77,881 Income, real estate, sales and other taxes 30,289 25,670 Other 52,259 55,707 $ 208,386 $ 233,405

CLOSURE AND POST-CLOSURE LIAB_2

CLOSURE AND POST-CLOSURE LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 through March 31, 2019 were as follows (in thousands): Landfill Non-Landfill Total Balance at January 1, 2019 $ 37,809 $ 32,122 $ 69,931 Liabilities assumed in acquisition — 98 98 New asset retirement obligations 719 — 719 Accretion 742 689 1,431 Changes in estimates recorded to statement of operations — 40 40 Changes in estimates recorded to balance sheet 2,798 — 2,798 Expenditures (163 ) (629 ) (792 ) Currency translation and other 50 146 196 Balance at March 31, 2019 $ 41,955 $ 32,466 $ 74,421

REMEDIAL LIABILITIES (Tables)

REMEDIAL LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2019
Environmental Remediation Obligations [Abstract]
Changes to remedial liabilities	The changes to remedial liabilities for the three months ended March 31, 2019 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, 2019 $ 1,838 $ 65,315 $ 53,864 $ 121,017 Accretion 22 675 446 1,143 Changes in estimates recorded to statement of operations 23 172 (1,009 ) (814 ) Expenditures (15 ) (1,154 ) (1,303 ) (2,472 ) Currency translation and other — 10 77 87 Balance at March 31, 2019 $ 1,868 $ 65,018 $ 52,075 $ 118,961

FINANCING ARRANGEMENTS (Tables)

FINANCING ARRANGEMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Summary of the entity's financial arrangements	The following table is a summary of the Company’s financing arrangements (in thousands): Current Obligations: March 31, 2019 December 31, 2018 Senior secured Term Loan Agreement ("Term Loan Agreement") $ 7,535 $ 7,535 Long-Term Obligations: Senior secured Term Loan Agreement due June 30, 2024 $ 732,813 $ 734,697 Senior unsecured notes, at 5.125%, due June 1, 2021 ("2021 Notes") 845,000 845,000 Long-term obligations, at par $ 1,577,813 $ 1,579,697 Unamortized debt issuance costs and premium, net (13,808 ) (14,676 ) Long-term obligations, at carrying value $ 1,564,005 $ 1,565,021

EARNINGS (LOSS) PER SHARE (Tabl

EARNINGS (LOSS) PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share computations	The following are computations of basic and diluted earnings (loss) per share (in thousands except for per share amounts): Three Months Ended March 31, 2019 2018 Numerator for basic and diluted earnings (loss) per share: Net income (loss) $ 976 $ (12,631 ) Denominator: Basic shares outstanding 55,848 56,457 Dilutive effect of stock-based compensation awards 234 — Dilutive shares outstanding 56,082 56,457 Basic income (loss) per share: $ 0.02 $ (0.22 ) Diluted income (loss) per share: $ 0.02 $ (0.22 )

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Schedule of accumulated other comprehensive loss	The changes in accumulated other comprehensive loss by component and related tax effects for the three months ended March 31, 2019 were as follows (in thousands): Foreign Currency Translation Unrealized Losses (Gains) on Available-For-Sale Securities Unrealized Losses on Interest Rate Hedge Unfunded Pension Liability Total Balance at January 1, 2019 $ (212,925 ) $ (69 ) $ (8,773 ) $ (1,604 ) $ (223,371 ) Other comprehensive income (loss) before tax effects 8,540 174 (5,017 ) — 3,697 Tax impact related to items in other comprehensive income (loss) — (31 ) — — (31 ) Amounts reclassified out of accumulated other comprehensive loss — — 358 — 358 Other comprehensive income (loss) 8,540 143 (4,659 ) — 4,024 Balance at March 31, 2019 $ (204,385 ) $ 74 $ (13,432 ) $ (1,604 ) $ (219,347 )
Reclassification out of accumulated other comprehensive income	The amounts reclassified out of accumulated other comprehensive loss into the consolidated statement of operations, with presentation location, during the three months ended March 31, 2019 were as follows (in thousands): For the Three Months Ended March 31, 2019 Other Comprehensive Income (Loss) Components Location Unrealized loss on interest rate hedge $ (358 ) Interest expense, net of interest income

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of restricted stock awards	The following table summarizes information about restricted stock awards for the three months ended March 31, 2019 : Restricted Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2019 657,240 $ 54.65 Granted 42,300 61.18 Vested (61,391 ) 52.83 Forfeited (21,870 ) 54.39 Balance at March 31, 2019 616,279 54.51
Summary of performance stock awards	The following table summarizes information about performance stock awards for the three months ended March 31, 2019 : Performance Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2019 213,490 $ 55.71 Granted — — Vested (51,996 ) 55.77 Forfeited (14,120 ) 55.69 Balance at March 31, 2019 147,374 55.69

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of Lease Expense	The Company’s lease expense was as follows (in thousands): For the Three Months Ended March 31, 2019 Operating lease cost $ 13,362 Finance lease cost Amortization of ROU asset 245 Interest on lease liability 321 Total finance lease cost 566 Short-term lease cost 19,714 Variable lease cost 1,242 Total lease cost $ 34,884 Weighted Average Remaining Lease Term (years) March 31, 2019 Operating leases 5.3 Finance lease 23.3 Weighted Average Discount Rate Operating leases 5.42 % Finance lease 5.25 %
Supplemental Lease Balance Sheet Information	Other information related to leases was as follows (in thousands, except lease term and discount rate): Supplemental Lease Balance Sheet Information: March 31, 2019 ROU assets Operating leases $ 170,550 Finance lease (included in property, plant and equipment, net) 22,782 Current portion of lease liabilities Operating leases 43,858 Finance lease (included in accrued expenses) 413 Long-term portion of lease liabilities Operating leases 128,689 Finance lease (included in deferred taxes, unrecognized tax benefits and other long-term liabilities) 23,797
Schedule of Operating Lease Maturity	At March 31, 2019 , our future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands): Years Ending December 31, Operating Leases Finance Lease 2019 (nine months) $ 40,019 $ 1,307 2020 44,558 1,777 2021 33,147 1,813 2022 26,081 1,849 2023 18,498 1,886 2024 12,525 1,923 Thereafter 26,037 40,636 Total future lease payments 200,865 51,191 Amount representing interest (28,318 ) (26,981 ) Total lease liabilities $ 172,547 $ 24,210
Schedule of Finance Lease Maturity	At March 31, 2019 , our future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands): Years Ending December 31, Operating Leases Finance Lease 2019 (nine months) $ 40,019 $ 1,307 2020 44,558 1,777 2021 33,147 1,813 2022 26,081 1,849 2023 18,498 1,886 2024 12,525 1,923 Thereafter 26,037 40,636 Total future lease payments 200,865 51,191 Amount representing interest (28,318 ) (26,981 ) Total lease liabilities $ 172,547 $ 24,210
Summary of Future Minimum Payments Under Operating Leases	The following is a summary of future minimum payments under operating leases that have initial or remaining non-cancelable lease terms in excess of one year at December 31, 2018 (in thousands): Year Total Operating Leases 2019 $ 56,480 2020 45,467 2021 33,564 2022 24,509 2023 15,253 Thereafter 35,778 Total minimum lease payments $ 211,051

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Reconciliation of third party revenues to direct revenues	The following table reconciles third-party revenues to direct revenues for the three months ended March 31, 2019 and March 31, 2018 (in thousands): For the Three Months Ended March 31, 2019 For the Three Months Ended March 31, 2018 Third-party revenues Intersegment revenues, net Corporate Items, net Direct revenues Third-party revenues Intersegment revenues, net Corporate Items, net Direct revenues Environmental Services $ 473,698 $ 34,075 $ 1,249 $ 509,022 $ 439,688 $ 31,965 $ 794 $ 472,447 Safety-Kleen 306,547 (34,075 ) 5 272,477 309,918 (31,965 ) 11 277,964 Corporate Items 594 — (1,254 ) (660 ) 172 — (805 ) (633 ) Total $ 780,839 $ — $ — $ 780,839 $ 749,778 $ — $ — $ 749,778
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 March 31, 2019 2018 Adjusted EBITDA: Environmental Services $ 89,510 $ 61,417 Safety-Kleen 54,793 61,884 Corporate Items (42,640 ) (35,036 ) Total 101,663 88,265 Reconciliation to Consolidated Statements of Operations: Accretion of environmental liabilities 2,574 2,430 Depreciation and amortization 75,355 74,844 Income from operations 23,734 10,991 Other (income) expense, net (2,983 ) 299 Interest expense, net of interest income 19,764 20,270 Income (loss) before provision for income taxes $ 6,953 $ (9,578 )
PP&E, intangible assets and total assets by segment	The following table presents certain assets by reportable segment and in the aggregate (in thousands): March 31, 2019 December 31, 2018 Property, plant and equipment, net Environmental Services $ 953,960 $ 951,867 Safety-Kleen 561,041 553,220 Corporate Items 73,612 56,891 Total property, plant and equipment, net $ 1,588,613 $ 1,561,978 Goodwill and Permits and other intangibles, net Environmental Services Goodwill $ 204,860 $ 207,019 Permits and other intangibles, net 95,040 93,313 Total Environmental Services 299,900 300,332 Safety-Kleen Goodwill $ 313,050 $ 307,170 Permits and other intangibles, net 343,918 348,562 Total Safety-Kleen 656,968 655,732 Total $ 956,868 $ 956,064
Schedule of assets by reported segment	The following table presents the total assets by reportable segment (in thousands): March 31, 2019 December 31, 2018 Environmental Services $ 1,724,208 $ 1,640,706 Safety-Kleen 1,518,723 1,431,381 Corporate Items 639,123 666,234 Total $ 3,882,054 $ 3,738,321
Total assets by geographical area	The following table presents the total assets by geographical area (in thousands): March 31, 2019 December 31, 2018 United States $ 3,212,979 $ 3,090,311 Canada 669,075 648,010 Total $ 3,882,054 $ 3,738,321

GUARANTOR AND NON-GUARANTOR S_2

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2019
Guarantor and Non-Guarantor Subsidiaries Financial Information [Abstract]
Schedule of condensed consolidating balance sheet	Following is the condensed consolidating balance sheet at March 31, 2019 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 27,431 $ 75,099 $ 64,841 $ — $ 167,371 Short-term marketable securities 121 — 57,356 — 57,477 Intercompany receivables 268,195 701,583 58,138 (1,027,916 ) — Accounts receivable, net — 526,047 87,460 — 613,507 Other current assets — 281,802 44,525 (16,560 ) 309,767 Property, plant and equipment, net — 1,261,206 327,407 — 1,588,613 Investments in subsidiaries 3,176,613 566,296 — (3,742,909 ) — Intercompany debt receivable — 14,900 21,000 (35,900 ) — Operating lease right-of-use assets — 137,591 32,959 — 170,550 Goodwill — 459,139 58,771 — 517,910 Permits and other intangibles, net — 390,838 48,120 — 438,958 Other long-term assets 1,437 13,530 2,903 31 17,901 Total assets $ 3,473,797 $ 4,428,031 $ 803,480 $ (4,823,254 ) $ 3,882,054 Liabilities and Stockholders’ Equity: Current liabilities $ 35,686 $ 431,891 $ 146,493 $ (16,560 ) $ 597,510 Intercompany payables 702,141 325,025 750 (1,027,916 ) — Closure, post-closure and remedial liabilities, net — 147,944 17,524 — 165,468 Long-term obligations, net 1,564,005 — — — 1,564,005 Operating lease liabilities, less current portion — 104,374 24,315 — 128,689 Intercompany debt payable — 21,000 14,900 (35,900 ) — Other long-term liabilities — 233,979 20,407 31 254,417 Total liabilities 2,301,832 1,264,213 224,389 (1,080,345 ) 2,710,089 Stockholders’ equity 1,171,965 3,163,818 579,091 (3,742,909 ) 1,171,965 Total liabilities and stockholders’ equity $ 3,473,797 $ 4,428,031 $ 803,480 $ (4,823,254 ) $ 3,882,054 Following is the condensed consolidating balance sheet at December 31, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 27,308 $ 101,302 $ 97,897 $ — $ 226,507 Short-term marketable securities 67 — 52,789 — 52,856 Intercompany receivables 262,475 721,521 60,693 (1,044,689 ) — Accounts receivable, net — 520,785 86,167 — 606,952 Other current assets — 289,869 49,631 (23,657 ) 315,843 Property, plant and equipment, net — 1,233,578 328,400 — 1,561,978 Investments in subsidiaries 3,162,704 571,304 — (3,734,008 ) — Intercompany debt receivable — 14,669 21,000 (35,669 ) — Goodwill — 456,307 57,882 — 514,189 Permits and other intangibles, net — 393,045 48,830 — 441,875 Other long-term assets 1,551 13,545 3,025 — 18,121 Total assets $ 3,454,105 $ 4,315,925 $ 806,314 $ (4,838,023 ) $ 3,738,321 Liabilities and Stockholders’ Equity: Current liabilities $ 20,170 $ 457,164 $ 148,601 $ (23,657 ) $ 602,278 Intercompany payables 699,158 321,846 23,685 (1,044,689 ) — Closure, post-closure and remedial liabilities, net — 151,480 16,434 — 167,914 Long-term obligations, net 1,565,021 — — — 1,565,021 Intercompany debt payable — 21,000 14,669 (35,669 ) — Other long-term liabilities — 212,924 20,428 — 233,352 Total liabilities 2,284,349 1,164,414 223,817 (1,104,015 ) 2,568,565 Stockholders’ equity 1,169,756 3,151,511 582,497 (3,734,008 ) 1,169,756 Total liabilities and stockholders’ equity $ 3,454,105 $ 4,315,925 $ 806,314 $ (4,838,023 ) $ 3,738,321
Schedule of condensed consolidating statement of income	Following is the consolidating statement of operations for the three months ended March 31, 2019 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 529,656 $ 144,139 $ (17,137 ) $ 656,658 Product revenues — 115,038 12,384 (3,241 ) 124,181 Total revenues — 644,694 156,523 (20,378 ) 780,839 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 356,590 124,030 (17,137 ) 463,483 Product cost of revenues — 99,357 4,765 (3,241 ) 100,881 Total cost of revenues — 455,947 128,795 (20,378 ) 564,364 Selling, general and administrative expenses 57 93,526 21,229 — 114,812 Accretion of environmental liabilities — 2,267 307 — 2,574 Depreciation and amortization — 57,335 18,020 — 75,355 (Loss) income from operations (57 ) 35,619 (11,828 ) — 23,734 Other income (expense), net 50 2,962 (29 ) — 2,983 Interest (expense) income, net (20,374 ) 9 601 — (19,764 ) Equity in earnings of subsidiaries, net of taxes 15,636 (13,336 ) — (2,300 ) — Intercompany interest income (expense) — 197 (197 ) — — (Loss) income before (benefit) provision for income taxes (4,745 ) 25,451 (11,453 ) (2,300 ) 6,953 (Benefit) provision for income taxes (5,721 ) 11,418 280 — 5,977 Net income (loss) 976 14,033 (11,733 ) (2,300 ) 976 Other comprehensive income 4,024 4,024 8,328 (12,352 ) 4,024 Comprehensive income (loss) $ 5,000 $ 18,057 $ (3,405 ) $ (14,652 ) $ 5,000 Following is the consolidating statement of operations for the three months ended March 31, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 481,483 $ 152,401 $ (14,165 ) $ 619,719 Product revenues — 121,582 11,450 (2,973 ) 130,059 Total revenues — 603,065 163,851 (17,138 ) 749,778 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 328,180 133,634 (14,165 ) 447,649 Product cost of revenues — 95,038 6,711 (2,973 ) 98,776 Total cost of revenues — 423,218 140,345 (17,138 ) 546,425 Selling, general and administrative expenses 35 93,843 21,210 — 115,088 Accretion of environmental liabilities — 2,176 254 — 2,430 Depreciation and amortization — 53,704 21,140 — 74,844 (Loss) income from operations (35 ) 30,124 (19,098 ) — 10,991 Other expense, net — (85 ) (214 ) — (299 ) Interest (expense) income, net (20,999 ) 505 224 — (20,270 ) Equity in earnings of subsidiaries, net of taxes 2,514 (20,062 ) — 17,548 — Intercompany interest income (expense) — 1,361 (1,361 ) — — (Loss) income before (benefit) provision for income taxes (18,520 ) 11,843 (20,449 ) 17,548 (9,578 ) (Benefit) provision for income taxes (5,889 ) 9,101 (159 ) — 3,053 Net (loss) income (12,631 ) 2,742 (20,290 ) 17,548 (12,631 ) Other comprehensive loss (16,746 ) (16,746 ) (14,007 ) 30,753 (16,746 ) Comprehensive loss $ (29,377 ) $ (14,004 ) $ (34,297 ) $ 48,301 $ (29,377 )
Schedule of condensed consolidating statement of cash flows	Following is the condensed consolidating statement of cash flows for the three months ended March 31, 2019 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash from operating activities $ 123 $ 50,344 $ (20,727 ) $ — $ 29,740 Cash flows used in investing activities: Additions to property, plant and equipment — (48,696 ) (10,251 ) — (58,947 ) Proceeds from sale and disposal of fixed assets — 3,366 955 — 4,321 Acquisitions, net of cash acquired — (14,870 ) — — (14,870 ) Additions to intangible assets including costs to obtain or renew permits — (1,294 ) 162 — (1,132 ) Proceeds from sale of available-for-sale securities — — 8,600 — 8,600 Purchases of available-for-sale securities — — (12,941 ) — (12,941 ) Intercompany — (10,484 ) — 10,484 — Net cash used in investing activities — (71,978 ) (13,475 ) 10,484 (74,969 ) Cash flows used in financing activities: Change in uncashed checks — (4,454 ) (315 ) — (4,769 ) Tax payments related to withholdings on vested restricted stock (2,276 ) — — — (2,276 ) Repurchases of common stock (6,324 ) — — — (6,324 ) Payments on finance lease — (115 ) — — (115 ) Principal payment on debt (1,884 ) — — — (1,884 ) Intercompany 10,484 — — (10,484 ) — Net cash used in financing activities — (4,569 ) (315 ) (10,484 ) (15,368 ) Effect of exchange rate change on cash — — 1,461 — 1,461 Increase (decrease) in cash and cash equivalents 123 (26,203 ) (33,056 ) — (59,136 ) Cash and cash equivalents, beginning of period 27,308 101,302 97,897 — 226,507 Cash and cash equivalents, end of period $ 27,431 $ 75,099 $ 64,841 $ — $ 167,371 Following is the condensed consolidating statement of cash flows for the three months ended March 31, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash from (used in) operating activities $ 143 $ 69,536 $ (17,776 ) $ — $ 51,903 Cash flows used in investing activities: Additions to property, plant and equipment — (37,319 ) (6,923 ) — (44,242 ) Proceeds from sale and disposal of fixed assets — 292 506 — 798 Acquisitions, net of cash acquired — (120,000 ) — — (120,000 ) Additions to intangible assets including costs to obtain or renew permits — (1,234 ) (11 ) — (1,245 ) Proceeds from sale of available-for-sale securities — — 3,264 — 3,264 Purchases of available-for-sale securities — — (3,003 ) — (3,003 ) Intercompany — (15,812 ) — 15,812 — Net cash used in investing activities — (174,073 ) (6,167 ) 15,812 (164,428 ) Cash flows used in financing activities: Change in uncashed checks — (3,578 ) (265 ) — (3,843 ) Tax payments related to withholdings on vested restricted stock (548 ) — — — (548 ) Repurchases of common stock (14,264 ) — — — (14,264 ) Principal payment on debt (1,000 ) — — — (1,000 ) Intercompany 15,812 — — (15,812 ) — Net cash used in financing activities — (3,578 ) (265 ) (15,812 ) (19,655 ) Effect of exchange rate change on cash — — (867 ) — (867 ) Increase (decrease) in cash and cash equivalents 143 (108,115 ) (25,075 ) — (133,047 ) Cash and cash equivalents, beginning of period 51,638 207,777 59,984 — 319,399 Cash and cash equivalents, end of period $ 51,781 $ 99,662 $ 34,909 $ — $ 186,352

SIGNIFICANT ACCOUNTING POLICI_3

SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset	$ 170,550
Total current and noncurrent lease liabilities	$ 172,547
Cumulative effect of change in accounting principle			$ (1,564)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		$ 185,500
Total current and noncurrent lease liabilities		$ 188,500
Accumulated Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			$ (1,564)
Real Estate Leases | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of leases (in years)	5 years
Real Estate Leases | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of leases (in years)	10 years
Non-Real Estate Leases | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of leases (in years)	2 years
Non-Real Estate Leases | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of leases (in years)	7 years
Short Term Leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of leases (in years)	1 year

REVENUES (Disaggregation of Rev

REVENUES (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total third party revenues	$ 780,839	$ 749,778
United States
Disaggregation of Revenue [Line Items]
Total third party revenues	675,337	631,759
Canada
Disaggregation of Revenue [Line Items]
Total third party revenues	105,502	118,019
Technical Services
Disaggregation of Revenue [Line Items]
Total third party revenues	251,919	236,306
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total third party revenues	71,626	69,935
Industrial Services
Disaggregation of Revenue [Line Items]
Total third party revenues	116,098	103,763
Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Total third party revenues	34,649	29,856
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total third party revenues	207,083	194,161
Safety-Kleen Oil (2)
Disaggregation of Revenue [Line Items]
Total third party revenues	99,464	115,757
Environmental Services
Disaggregation of Revenue [Line Items]
Total third party revenues	473,698	439,688
Environmental Services | United States
Disaggregation of Revenue [Line Items]
Total third party revenues	388,169	343,972
Environmental Services | Canada
Disaggregation of Revenue [Line Items]
Total third party revenues	85,529	95,716
Environmental Services | Technical Services
Disaggregation of Revenue [Line Items]
Total third party revenues	251,919	236,306
Environmental Services | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total third party revenues	71,626	69,935
Environmental Services | Industrial Services
Disaggregation of Revenue [Line Items]
Total third party revenues	116,098	103,763
Environmental Services | Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Total third party revenues	34,055	29,684
Environmental Services | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Environmental Services | Safety-Kleen Oil (2)
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Safety-Kleen
Disaggregation of Revenue [Line Items]
Total third party revenues	306,547	309,918
Safety-Kleen | United States
Disaggregation of Revenue [Line Items]
Total third party revenues	286,574	287,642
Safety-Kleen | Canada
Disaggregation of Revenue [Line Items]
Total third party revenues	19,973	22,276
Safety-Kleen | Technical Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Safety-Kleen | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Safety-Kleen | Industrial Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Safety-Kleen | Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Safety-Kleen | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total third party revenues	207,083	194,161
Safety-Kleen | Safety-Kleen Oil (2)
Disaggregation of Revenue [Line Items]
Total third party revenues	99,464	115,757
Corporate
Disaggregation of Revenue [Line Items]
Total third party revenues	594	172
Corporate | United States
Disaggregation of Revenue [Line Items]
Total third party revenues	594	145
Corporate | Canada
Disaggregation of Revenue [Line Items]
Total third party revenues	0	27
Corporate | Technical Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Corporate | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Corporate | Industrial Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Corporate | Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Total third party revenues	594	172
Corporate | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total third party revenues	0	0
Corporate | Safety-Kleen Oil (2)
Disaggregation of Revenue [Line Items]
Total third party revenues	$ 0	$ 0

REVENUES (Contract Balances) (D

REVENUES (Contract Balances) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Receivables	$ 613,507	$ 606,952
Contract assets (unbilled receivables)	42,513	54,794
Contract liabilities (deferred revenue)	$ 67,557	$ 61,843

REVENUES (Narrative) (Details)

REVENUES (Narrative) (Details) - Veolia Division $ in Millions	Feb. 23, 2018USD ($)
Business Acquisition [Line Items]
Acquired receivables	$ 21.5
Customer contracts
Business Acquisition [Line Items]
Acquired contract assets	$ 18.1

BUSINESS COMBINATIONS (2019 Acq

BUSINESS COMBINATIONS (2019 Acquisition) (Details) - USD ($) $ in Thousands	Mar. 01, 2019	Mar. 31, 2019
Business Acquisition [Line Items]
Goodwill recognized		$ 6,825
Private Held Company
Business Acquisition [Line Items]
Purchase price	$ 10,400
Goodwill recognized	$ 6,800

BUSINESS COMBINATIONS (2018 Acq

BUSINESS COMBINATIONS (2018 Acquisitions) (Details) - USD ($) $ in Thousands	Aug. 31, 2018	Feb. 23, 2018	Mar. 31, 2019
Business Acquisition [Line Items]
Goodwill recognized			$ 6,825
Acquired Company Included in Safety-Kleen and Environmental Services Segments
Business Acquisition [Line Items]
Goodwill recognized	$ 12,400
Purchase price	$ 27,300
Veolia Division
Business Acquisition [Line Items]
Purchase price		$ 124,500
Weighted average amortization period (in years)		8 years 2 months

BUSINESS COMBINATIONS (Assets A

BUSINESS COMBINATIONS (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 517,910	$ 514,189
Veolia Division
Business Acquisition [Line Items]
Accounts receivable	39,558
Inventories and supplies	1,126
Prepaid and other current assets	828
Property, plant and equipment	72,243
Permits and other intangibles	5,140
Current liabilities	(18,372)
Closure and post-closure liabilities	(354)
Total identifiable net assets	100,169
Goodwill	24,331
Total purchase price, net of cash acquired	$ 124,500

INVENTORIES AND SUPPLIES (Detai

INVENTORIES AND SUPPLIES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Oil and oil products	$ 67,888	$ 70,823
Supplies and drums	108,976	104,609
Solvent and solutions	10,500	10,657
Other	13,450	13,390
Total inventories and supplies	$ 200,814	$ 199,479

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 3,424,237	$ 3,332,595
Less - accumulated depreciation and amortization	1,835,624	1,770,617
Total property, plant and equipment, net	1,588,613	1,561,978
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	129,684	123,734
Asset retirement costs (non-landfill)
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	15,258	15,148
Landfill assets
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	160,093	154,918
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	465,707	440,188
Camp equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	156,031	152,998
Vehicles
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	753,490	721,735
Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	1,711,470	1,697,490
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	5,476	5,453
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 27,028	$ 20,931

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Interest costs capitalized adjustment	$ 0.1	$ 0.3
Depreciation inclusive of amortization	$ 65.9	$ 65.6

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS (Rollforward of Goodwill) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Goodwill [Roll Forward]
Balance at beginning of year	$ 514,189
Increase from current period acquisitions	6,825
Measurement period adjustments from prior period acquisitions	(3,993)
Foreign currency translation	889
Balance at end of year	517,910
Environmental Services
Goodwill [Roll Forward]
Balance at beginning of year	207,019
Increase from current period acquisitions	0
Measurement period adjustments from prior period acquisitions	(2,571)
Foreign currency translation	412
Balance at end of year	204,860
Safety-Kleen
Goodwill [Roll Forward]
Balance at beginning of year	307,170
Increase from current period acquisitions	6,825
Measurement period adjustments from prior period acquisitions	(1,422)
Foreign currency translation	477
Balance at end of year	$ 313,050

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS (Amortizable Other Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	$ 616,028	$ 608,332
Accumulated Amortization	299,693	288,925
Net	316,335	319,407
Total permits and other intangible assets, Cost	738,651	730,800
Total permits and other intangible assets, Net	438,958	441,875
Trademarks and trade names
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Trademarks and trade names	122,623	122,468
Permits
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	180,463	177,583
Accumulated Amortization	81,135	79,358
Net	99,328	98,225
Customer and supplier relationships
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	397,949	393,487
Accumulated Amortization	187,195	179,824
Net	210,754	213,663
Other intangible assets
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	37,616	37,262
Accumulated Amortization	31,363	29,743
Net	$ 6,253	$ 7,519

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of permits and other intangible assets	$ 9.5	$ 9.2

GOODWILL AND OTHER INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLE ASSETS (Expected Future Amortization) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
2019 (nine months)	$ 24,947
2020	31,289
2021	28,020
2022	27,849
2023	23,862
Thereafter	180,368
Net	$ 316,335	$ 319,407

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Insurance	$ 64,298	$ 70,217
Interest	14,783	3,930
Accrued compensation and benefits	46,757	77,881
Income, real estate, sales and other taxes	30,289	25,670
Other	52,259	55,707
Total accrued expenses	$ 208,386	$ 233,405

CLOSURE AND POST-CLOSURE LIAB_3

CLOSURE AND POST-CLOSURE LIABILITIES (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Changes to post-closure liabilities
Beginning balance	$ 69,931
Liabilities assumed in acquisition	98
New asset retirement obligations	719
Accretion	1,431
Changes in estimates recorded to statement of operations	40
Changes in estimates recorded to balance sheet	2,798
Expenditures	(792)
Currency translation and other	196
Ending balance	$ 74,421
Credit-adjusted risk-free rate	6.02%
Landfill Retirement Liability
Changes to post-closure liabilities
Beginning balance	$ 37,809
Liabilities assumed in acquisition	0
New asset retirement obligations	719
Accretion	742
Changes in estimates recorded to statement of operations	0
Changes in estimates recorded to balance sheet	2,798
Expenditures	(163)
Currency translation and other	50
Ending balance	41,955
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Beginning balance	32,122
Liabilities assumed in acquisition	98
New asset retirement obligations	0
Accretion	689
Changes in estimates recorded to statement of operations	40
Changes in estimates recorded to balance sheet	0
Expenditures	(629)
Currency translation and other	146
Ending balance	$ 32,466

REMEDIAL LIABILITIES (Details)

REMEDIAL LIABILITIES (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	$ 121,017
Accretion	1,143
Changes in estimates recorded to statement of operations	(814)
Expenditures	(2,472)
Currency translation and other	87
Balance at end of year	118,961
Remedial Liabilities for Landfill Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	1,838
Accretion	22
Changes in estimates recorded to statement of operations	23
Expenditures	(15)
Currency translation and other	0
Balance at end of year	1,868
Remedial Liabilities for Inactive Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	65,315
Accretion	675
Changes in estimates recorded to statement of operations	172
Expenditures	(1,154)
Currency translation and other	10
Balance at end of year	65,018
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	53,864
Accretion	446
Changes in estimates recorded to statement of operations	(1,009)
Expenditures	(1,303)
Currency translation and other	77
Balance at end of year	$ 52,075

FINANCING ARRANGEMENTS (Summary

FINANCING ARRANGEMENTS (Summary of Financing Arrangements) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Current portion of long-term obligations	$ 7,535	$ 7,535
Long-term obligations, at par	1,577,813	1,579,697
Unamortized debt issuance costs and premium, net	(13,808)	(14,676)
Long-term obligations, at carrying value	1,564,005	1,565,021
Secured debt | Term Loan Agreement
Debt Instrument [Line Items]
Current portion of long-term obligations	7,535	7,535
Long-term obligations, at par	732,813	734,697
Unsecured debt | Senior unsecured notes, at 5.125%, due June 1, 2021 (2021 Notes)
Debt Instrument [Line Items]
Long-term obligations, at par	$ 845,000	$ 845,000
Interest rate	5.125%

FINANCING ARRANGEMENTS (Narrati

FINANCING ARRANGEMENTS (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Available to borrow and outstanding letters of credit	$ 209,100,000	$ 235,400,000
Outstanding letters of credit	$ 153,300,000	130,100,000
Effective interest rate percentage	4.67%
Derivative liability	$ 13,400,000	8,800,000
Term Loan Agreement
Debt Instrument [Line Items]
Debt outstanding	740,300,000
Term Loans with Interest Rate Swap Agreements
Debt Instrument [Line Items]
Debt outstanding	350,000,000
Secured debt | Term Loan Agreement
Debt Instrument [Line Items]
Debt fair value	$ 738,500,000	707,000,000
Unsecured debt | Senior unsecured notes, at 5.125%, due June 1, 2021 (2021 Notes)
Debt Instrument [Line Items]
Interest rate	5.125%
Debt fair value	$ 846,100,000	$ 845,000,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity	$ 400,000,000
Eurodollar
Debt Instrument [Line Items]
Interest rate percentage	1.75%
Interest Rate Swap
Debt Instrument [Line Items]
Notional amount of interest rate swap agreements	$ 350,000,000
Interest rate percentage	2.92%

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate	86.00%	(31.90%)
Unrecognized tax benefits	$ 3.2
Interest on unrecognized tax benefits	0.8
Reduction in unrecognized tax benefits from expiring statue of limitations	$ 0.6

EARNINGS (LOSS) PER SHARE (Comp

EARNINGS (LOSS) PER SHARE (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator for basic and diluted earnings (loss) per share:
Net income (loss)	$ 976	$ (12,631)
Denominator:
Basic shares outstanding (in shares)	55,848	56,457
Dilutive effect of equity-based compensation awards (in shares)	234	0
Dilutive shares outstanding (in shares)	56,082	56,457
Basic income (loss) per share (in USD per share)	$ 0.02	$ (0.22)
Diluted income (loss) per share (in USD per share)	$ 0.02	$ (0.22)

EARNINGS (LOSS) PER SHARE (Narr

EARNINGS (LOSS) PER SHARE (Narrative) (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
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)	78,271	896,180
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)	27,357

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS (Changes in Accumulated Other Comprehensive Loss by Component) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,169,756
Other comprehensive income (loss) before tax effects	3,697
Tax impact related to items in other comprehensive income (loss)	(31)
Amounts reclassified out of accumulated other comprehensive loss	358
Other comprehensive income	4,024
Balance at end of period	1,171,965
Foreign Currency Translation
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(212,925)
Other comprehensive income (loss) before tax effects	8,540
Tax impact related to items in other comprehensive income (loss)	0
Amounts reclassified out of accumulated other comprehensive loss	0
Other comprehensive income	8,540
Balance at end of period	(204,385)
Unrealized Losses (Gains) on Available-For-Sale Securities
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(69)
Other comprehensive income (loss) before tax effects	174
Tax impact related to items in other comprehensive income (loss)	(31)
Amounts reclassified out of accumulated other comprehensive loss	0
Other comprehensive income	143
Balance at end of period	74
Unrealized Losses on Interest Rate Hedge
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(8,773)
Other comprehensive income (loss) before tax effects	(5,017)
Tax impact related to items in other comprehensive income (loss)	0
Amounts reclassified out of accumulated other comprehensive loss	358
Other comprehensive income	(4,659)
Balance at end of period	(13,432)
Unfunded Pension Liability
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(1,604)
Other comprehensive income (loss) before tax effects	0
Tax impact related to items in other comprehensive income (loss)	0
Amounts reclassified out of accumulated other comprehensive loss	0
Other comprehensive income	0
Balance at end of period	(1,604)
Total
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(223,371)
Balance at end of period	$ (219,347)

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE LOSS (Reclassified Out of Accumulated Other Comprehensive Loss) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	$ 976,000	$ (12,631,000)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)		$ 0
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	$ (358,000)

STOCK-BASED COMPENSATION (Narra

STOCK-BASED COMPENSATION (Narrative) (Details) - USD ($) shares in Thousands	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		$ 5,800,000	$ 3,100,000
Income tax benefit		1,100,000	$ 900,000
Authorized common stock repurchase amount	$ 600,000,000	$ 600,000,000
Repurchases of common stock (in shares)	5,700	97	280
Repurchases of common stock	$ 300,300,000	$ 6,324,000	$ 14,264,000
Remaining amount for repurchase under program				$ 299,700,000
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	23,100,000	$ 23,100,000
Period for recognition (in years)		2 years 7 months
Fair value restricted stock		$ 3,200,000	1,300,000
Performance stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 4,600,000	4,600,000
Fair value restricted stock		$ 2,900,000	$ 500,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)		3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)		5 years

STOCK-BASED COMPENSATION (Restr

STOCK-BASED COMPENSATION (Restricted Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restricted stock awards
Number of Shares
Beginning balance (in shares)	657,240
Granted (in shares)	42,300
Vested (in shares)	(61,391)
Forfeited (in shares)	(21,870)
Ending balance (in shares)	616,279
Weighted Average Grant-Date Fair Value
Beginning of period (in USD per share)	$ 54.65
Granted (in USD per share)	61.18
Vested (in USD per share)	52.83
Forfeited (in USD per share)	54.39
End of period (in USD per share)	$ 54.51
Unrecognized compensation cost	$ 23.1
Period for recognition (in years)	2 years 7 months
Fair value restricted stock	$ 3.2	$ 1.3
Minimum
Weighted Average Grant-Date Fair Value
Vesting period (in years)	3 years
Maximum
Weighted Average Grant-Date Fair Value
Vesting period (in years)	5 years

STOCK-BASED COMPENSATION (Perfo

STOCK-BASED COMPENSATION (Performance Stock Awards (Details) - Performance stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of Shares
Beginning balance (in shares)	213,490
Granted (in shares)	0
Vested (in shares)	(51,996)
Forfeited (in shares)	(14,120)
Ending balance (in shares)	147,374
Weighted Average Grant-Date Fair Value
Beginning of period (in USD per share)	$ 55.71
Granted (in USD per share)	0
Vested (in USD per share)	55.77
Forfeited (in USD per share)	55.69
End of period (in USD per share)	$ 55.69
Unrecognized compensation cost	$ 4.6
Fair value restricted stock	$ 2.9	$ 0.5

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019USD ($)siteproceedingclaim	Dec. 31, 2012CAD ($)	Dec. 31, 1999municipality	Dec. 31, 1968permit	Dec. 31, 2018USD ($)proceeding
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities | $	$ 23,800,000				$ 25,400,000
Number of proceedings as defendant | proceeding	67
Number of product liability claims settled or dismissed | claim	7
Legal and Administrative Proceedings
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities | $	$ 17,600,000				17,900,000
Possible increase in legal and administrative proceedings | $	$ 1,800,000
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
Superfund Proceedings
Contingencies [Line Items]
Number of sites owned by third party excluded from cleanup or related liabilities	128
Number of sites owned by the entity subject to proceedings under federal or state superfund laws	5
Number of sites owned by third parties	123
Number of sites for which environmental remediation expense is settled	30
Third party sites requiring expenditure on remediation	16
Number of sites not currently requiring expenditures on remediation	77
Number of sites which potential liability could exceed $100,000	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 | $	$ 6,200,000				$ 7,500,000
Number of proceedings as defendant | proceeding	11				10
Federal and State Enforcement Actions | Minimum
Contingencies [Line Items]
Minimum potential liability | $	$ 100,000				$ 100,000

LEASES - Lease Expense (Details

LEASES - Lease Expense (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating lease cost	$ 13,362
Finance lease cost
Amortization of ROU asset	245
Interest on lease liability	321
Total finance lease cost	566
Short-term lease cost	19,714
Variable lease cost	1,242
Total lease cost	$ 34,884

LEASES - Supplemental Cash Flow

LEASES - Supplemental Cash Flow Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 13,554
Financing cash flows from finance lease	$ 115

LEASES - Supplemental Finance L

LEASES - Supplemental Finance Lease Balance Sheet information (Details) $ in Thousands	Mar. 31, 2019USD ($)
ROU assets
Operating leases	$ 170,550
Finance lease (included in property, plant and equipment, net)	22,782
Current portion of lease liabilities
Operating leases	43,858
Finance lease (included in accrued expenses)	413
Long-term portion of lease liabilities
Operating leases	128,689
Finance lease (included in deferred taxes, unrecognized tax benefits and other long-term liabilities)	$ 23,797

LEASES - Leases Other Informati

LEASES - Leases Other Information (Details)	Mar. 31, 2019
Weighted Average Remaining Lease Term (years)
Operating leases (in years)	5 years 3 months
Finance leases (in years)	23 years 3 months
Weighted Average Discount Rate
Operating leases (as a percentage)	5.42%
Finance leases (as a percentage)	5.25%

LEASES - Schedule of Future Lea

LEASES - Schedule of Future Lease Payments (Details) $ in Thousands	Mar. 31, 2019USD ($)
Operating Leases
2019 (remaining nine months)	$ 40,019
2020	44,558
2021	33,147
2022	26,081
2023	18,498
2024	12,525
Thereafter	26,037
Total future lease payments	200,865
Amount representing interest	(28,318)
Total lease liabilities	172,547
Finance Lease
2019 (remaining nine months)	1,307
2020	1,777
2021	1,813
2022	1,849
2023	1,886
2024	1,923
Thereafter	40,636
Total future lease payments	51,191
Amount representing interest	(26,981)
Total lease liabilities	$ 24,210

LEASES - Summary of Future Mini

LEASES - Summary of Future Minimum Payments Under Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2019
Leases [Abstract]
2019				$ 56,480
2020				45,467
2021				33,564
2022				24,509
2023				15,253
Thereafter				35,778
Total minimum lease payments				$ 211,051
Rent expense	$ 141,100	$ 125,400	$ 121,900

SEGMENT REPORTING (Narrative) (

SEGMENT REPORTING (Narrative) (Details)	3 Months Ended
	Mar. 31, 2019segment
Segment Reporting [Abstract]
Number of operating segments	2

SEGMENT REPORTING (Third Party

SEGMENT REPORTING (Third Party Revenues to Direct Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 780,839	$ 749,778
Direct revenues
Segment Reporting Information [Line Items]
Total revenues	780,839	749,778
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	473,698	439,688
Environmental Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	34,075	31,965
Environmental Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	1,249	794
Environmental Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	509,022	472,447
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	306,547	309,918
Safety-Kleen | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(34,075)	(31,965)
Safety-Kleen | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	5	11
Safety-Kleen | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	272,477	277,964
Corporate
Segment Reporting Information [Line Items]
Total revenues	594	172
Corporate | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(1,254)	(805)
Corporate | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	$ (660)	$ (633)

SEGMENT REPORTING (Adjusted EBI

SEGMENT REPORTING (Adjusted EBITDA Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 101,663	$ 88,265
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,574	2,430
Depreciation and amortization	75,355	74,844
Income from operations	23,734	10,991
Other (income) expense, net	(2,983)	299
Interest expense, net of interest income	19,764	20,270
Income (loss) before provision for income taxes	6,953	(9,578)
Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	89,510	61,417
Safety-Kleen
Segment Reporting Information [Line Items]
Adjusted EBITDA	54,793	61,884
Corporate Items
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (42,640)	$ (35,036)

SEGMENT REPORTING (Assets by Re

SEGMENT REPORTING (Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,588,613	$ 1,561,978
Goodwill	517,910	514,189
Permits and other intangibles, net	438,958	441,875
Total assets	3,882,054	3,738,321
Intangible Assets, Net (Including Goodwill)	956,868	956,064
Environmental Services
Segment Reporting Information [Line Items]
Goodwill	204,860	207,019
Safety-Kleen
Segment Reporting Information [Line Items]
Goodwill	313,050	307,170
Direct revenues | Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	953,960	951,867
Goodwill	204,860	207,019
Permits and other intangibles, net	95,040	93,313
Total assets	1,724,208	1,640,706
Intangible Assets, Net (Including Goodwill)	299,900	300,332
Direct revenues | Safety-Kleen
Segment Reporting Information [Line Items]
Property, plant and equipment, net	561,041	553,220
Goodwill	313,050	307,170
Permits and other intangibles, net	343,918	348,562
Total assets	1,518,723	1,431,381
Intangible Assets, Net (Including Goodwill)	656,968	655,732
Corporate Items, net
Segment Reporting Information [Line Items]
Property, plant and equipment, net	73,612	56,891
Total assets	$ 639,123	$ 666,234

SEGMENT REPORTING (Total Assets

SEGMENT REPORTING (Total Assets by Geographical Area) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 3,882,054	$ 3,738,321
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	3,212,979	3,090,311
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 669,075	$ 648,010

GUARANTOR AND NON-GUARANTOR S_3

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Narrative) (Details)	3 Months Ended
	Mar. 31, 2019
Guarantor and Non-Guarantor Subsidiaries Financial Information [Abstract]
Ownership percentage of U.S. guarantor subsidiaries	100.00%

GUARANTOR AND NON-GUARANTOR S_4

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 167,371	$ 226,507	$ 186,352	$ 319,399
Short-term marketable securities	57,477	52,856
Intercompany receivables	0	0
Accounts receivable, net	613,507	606,952
Other current assets	309,767	315,843
Property, plant and equipment, net	1,588,613	1,561,978
Investments in subsidiaries	0	0
Intercompany debt receivable	0	0
Operating lease right-of-use asset	170,550
Goodwill	517,910	514,189
Permits and other intangibles, net	438,958	441,875
Other long-term assets	17,901	18,121
Total assets	3,882,054	3,738,321
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	597,510	602,278
Intercompany payables	0	0
Closure, post-closure and remedial liabilities, net	165,468	167,914
Long-term obligations, less current portion	1,564,005	1,565,021
Operating lease liabilities, less current portion	128,689
Intercompany debt payable	0	0
Other long-term liabilities	254,417	233,352
Total liabilities	2,710,089	2,568,565
Stockholders’ equity	1,171,965	1,169,756	1,145,526	1,188,202
Total liabilities and stockholders’ equity	3,882,054	3,738,321
Reportable Legal Entities | Clean Harbors, Inc.
ASSETS
Cash and cash equivalents	27,431	27,308	51,781	51,638
Short-term marketable securities	121	67
Intercompany receivables	268,195	262,475
Accounts receivable, net	0	0
Other current assets	0	0
Property, plant and equipment, net	0	0
Investments in subsidiaries	3,176,613	3,162,704
Intercompany debt receivable	0	0
Operating lease right-of-use asset	0
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	1,437	1,551
Total assets	3,473,797	3,454,105
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	35,686	20,170
Intercompany payables	702,141	699,158
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	1,564,005	1,565,021
Operating lease liabilities, less current portion	0
Intercompany debt payable	0	0
Other long-term liabilities	0	0
Total liabilities	2,301,832	2,284,349
Stockholders’ equity	1,171,965	1,169,756
Total liabilities and stockholders’ equity	3,473,797	3,454,105
Reportable Legal Entities | Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	75,099	101,302	99,662	207,777
Short-term marketable securities	0	0
Intercompany receivables	701,583	721,521
Accounts receivable, net	526,047	520,785
Other current assets	281,802	289,869
Property, plant and equipment, net	1,261,206	1,233,578
Investments in subsidiaries	566,296	571,304
Intercompany debt receivable	14,900	14,669
Operating lease right-of-use asset	137,591
Goodwill	459,139	456,307
Permits and other intangibles, net	390,838	393,045
Other long-term assets	13,530	13,545
Total assets	4,428,031	4,315,925
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	431,891	457,164
Intercompany payables	325,025	321,846
Closure, post-closure and remedial liabilities, net	147,944	151,480
Long-term obligations, less current portion	0	0
Operating lease liabilities, less current portion	104,374
Intercompany debt payable	21,000	21,000
Other long-term liabilities	233,979	212,924
Total liabilities	1,264,213	1,164,414
Stockholders’ equity	3,163,818	3,151,511
Total liabilities and stockholders’ equity	4,428,031	4,315,925
Reportable Legal Entities | Non-Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	64,841	97,897	34,909	59,984
Short-term marketable securities	57,356	52,789
Intercompany receivables	58,138	60,693
Accounts receivable, net	87,460	86,167
Other current assets	44,525	49,631
Property, plant and equipment, net	327,407	328,400
Investments in subsidiaries	0	0
Intercompany debt receivable	21,000	21,000
Operating lease right-of-use asset	32,959
Goodwill	58,771	57,882
Permits and other intangibles, net	48,120	48,830
Other long-term assets	2,903	3,025
Total assets	803,480	806,314
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	146,493	148,601
Intercompany payables	750	23,685
Closure, post-closure and remedial liabilities, net	17,524	16,434
Long-term obligations, less current portion	0	0
Operating lease liabilities, less current portion	24,315
Intercompany debt payable	14,900	14,669
Other long-term liabilities	20,407	20,428
Total liabilities	224,389	223,817
Stockholders’ equity	579,091	582,497
Total liabilities and stockholders’ equity	803,480	806,314
Consolidating Adjustments
ASSETS
Cash and cash equivalents	0	0	$ 0	$ 0
Short-term marketable securities	0	0
Intercompany receivables	(1,027,916)	(1,044,689)
Accounts receivable, net	0	0
Other current assets	(16,560)	(23,657)
Property, plant and equipment, net	0	0
Investments in subsidiaries	(3,742,909)	(3,734,008)
Intercompany debt receivable	(35,900)	(35,669)
Operating lease right-of-use asset	0
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	31	0
Total assets	(4,823,254)	(4,838,023)
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	(16,560)	(23,657)
Intercompany payables	(1,027,916)	(1,044,689)
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	0	0
Operating lease liabilities, less current portion	0
Intercompany debt payable	(35,900)	(35,669)
Other long-term liabilities	31	0
Total liabilities	(1,080,345)	(1,104,015)
Stockholders’ equity	(3,742,909)	(3,734,008)
Total liabilities and stockholders’ equity	$ (4,823,254)	$ (4,838,023)

GUARANTOR AND NON-GUARANTOR S_5

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Consolidating Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Total revenues	$ 780,839	$ 749,778
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	564,364	546,425
Selling, general and administrative expenses	114,812	115,088
Accretion of environmental liabilities	2,574	2,430
Depreciation and amortization	75,355	74,844
Income from operations	23,734	10,991
Other income (expense), net	2,983	(299)
Interest (expense) income, net	(19,764)	(20,270)
Equity in earnings of subsidiaries, net of taxes	0	0
Intercompany interest income (expense)	0	0
Income (loss) before provision for income taxes	6,953	(9,578)
(Benefit) provision for income taxes	5,977	3,053
Net income (loss)	976	(12,631)
Other comprehensive income	4,024	(16,746)
Comprehensive income (loss)	5,000	(29,377)
Reportable Legal Entities | Clean Harbors, Inc.
Revenues:
Total revenues	0	0
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	0	0
Selling, general and administrative expenses	57	35
Accretion of environmental liabilities	0	0
Depreciation and amortization	0	0
Income from operations	(57)	(35)
Other income (expense), net	50	0
Interest (expense) income, net	(20,374)	(20,999)
Equity in earnings of subsidiaries, net of taxes	15,636	2,514
Intercompany interest income (expense)	0	0
Income (loss) before provision for income taxes	(4,745)	(18,520)
(Benefit) provision for income taxes	(5,721)	(5,889)
Net income (loss)	976	(12,631)
Other comprehensive income	4,024	(16,746)
Comprehensive income (loss)	5,000	(29,377)
Reportable Legal Entities | Guarantor Subsidiaries
Revenues:
Total revenues	644,694	603,065
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	455,947	423,218
Selling, general and administrative expenses	93,526	93,843
Accretion of environmental liabilities	2,267	2,176
Depreciation and amortization	57,335	53,704
Income from operations	35,619	30,124
Other income (expense), net	2,962	(85)
Interest (expense) income, net	9	505
Equity in earnings of subsidiaries, net of taxes	(13,336)	(20,062)
Intercompany interest income (expense)	197	1,361
Income (loss) before provision for income taxes	25,451	11,843
(Benefit) provision for income taxes	11,418	9,101
Net income (loss)	14,033	2,742
Other comprehensive income	4,024	(16,746)
Comprehensive income (loss)	18,057	(14,004)
Reportable Legal Entities | Non-Guarantor Subsidiaries
Revenues:
Total revenues	156,523	163,851
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	128,795	140,345
Selling, general and administrative expenses	21,229	21,210
Accretion of environmental liabilities	307	254
Depreciation and amortization	18,020	21,140
Income from operations	(11,828)	(19,098)
Other income (expense), net	(29)	(214)
Interest (expense) income, net	601	224
Equity in earnings of subsidiaries, net of taxes	0	0
Intercompany interest income (expense)	(197)	(1,361)
Income (loss) before provision for income taxes	(11,453)	(20,449)
(Benefit) provision for income taxes	280	(159)
Net income (loss)	(11,733)	(20,290)
Other comprehensive income	8,328	(14,007)
Comprehensive income (loss)	(3,405)	(34,297)
Consolidating Adjustments
Revenues:
Total revenues	(20,378)	(17,138)
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	(20,378)	(17,138)
Selling, general and administrative expenses	0	0
Accretion of environmental liabilities	0	0
Depreciation and amortization	0	0
Income from operations	0	0
Other income (expense), net	0	0
Interest (expense) income, net	0	0
Equity in earnings of subsidiaries, net of taxes	(2,300)	17,548
Intercompany interest income (expense)	0	0
Income (loss) before provision for income taxes	(2,300)	17,548
(Benefit) provision for income taxes	0	0
Net income (loss)	(2,300)	17,548
Other comprehensive income	(12,352)	30,753
Comprehensive income (loss)	(14,652)	48,301
Service
Revenues:
Total revenues	656,658	619,719
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	463,483	447,649
Service | Reportable Legal Entities | Clean Harbors, Inc.
Revenues:
Total revenues	0	0
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	0	0
Service | Reportable Legal Entities | Guarantor Subsidiaries
Revenues:
Total revenues	529,656	481,483
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	356,590	328,180
Service | Reportable Legal Entities | Non-Guarantor Subsidiaries
Revenues:
Total revenues	144,139	152,401
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	124,030	133,634
Service | Consolidating Adjustments
Revenues:
Total revenues	(17,137)	(14,165)
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	(17,137)	(14,165)
Product
Revenues:
Total revenues	124,181	130,059
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	100,881	98,776
Product | Reportable Legal Entities | Clean Harbors, Inc.
Revenues:
Total revenues	0	0
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	0	0
Product | Reportable Legal Entities | Guarantor Subsidiaries
Revenues:
Total revenues	115,038	121,582
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	99,357	95,038
Product | Reportable Legal Entities | Non-Guarantor Subsidiaries
Revenues:
Total revenues	12,384	11,450
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	4,765	6,711
Product | Consolidating Adjustments
Revenues:
Total revenues	(3,241)	(2,973)
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ (3,241)	$ (2,973)

GUARANTOR AND NON-GUARANTOR S_6

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed consolidating statement of cash flows
Net cash from operating activities	$ 29,740	$ 51,903
Cash flows used in investing activities:
Additions to property, plant and equipment	(58,947)	(44,242)
Proceeds from sale and disposal of fixed assets	4,321	798
Acquisitions, net of cash acquired	(14,870)	(120,000)
Additions to intangible assets including costs to obtain or renew permits	(1,132)	(1,245)
Proceeds from sale of available-for-sale securities	8,600
Purchases of available-for-sale securities	(12,941)
Proceeds from sale of available-for-sale securities		3,264
Purchases of available-for-sale securities		(3,003)
Intercompany	0	0
Net cash used in investing activities	(74,969)	(164,428)
Cash flows used in financing activities:
Change in uncashed checks	(4,769)	(3,843)
Tax payments related to withholdings on vested restricted stock	(2,276)	(548)
Repurchases of common stock	(6,324)	(14,264)
Payments on finance lease	(115)
Principal payments on debt	(1,884)	(1,000)
Intercompany	0	0
Net cash used in financing activities	(15,368)	(19,655)
Effect of exchange rate change on cash	1,461	(867)
Decrease in cash and cash equivalents	(59,136)	(133,047)
Cash and cash equivalents, beginning of period	226,507	319,399
Cash and cash equivalents, end of period	167,371	186,352
Consolidating Adjustments
Condensed consolidating statement of cash flows
Net cash from operating activities	0	0
Cash flows used in investing activities:
Additions to property, plant and equipment	0	0
Proceeds from sale and disposal of fixed assets	0	0
Acquisitions, net of cash acquired	0	0
Additions to intangible assets including costs to obtain or renew permits	0	0
Proceeds from sale of available-for-sale securities	0
Purchases of available-for-sale securities	0
Proceeds from sale of available-for-sale securities		0
Purchases of available-for-sale securities		0
Intercompany	10,484	15,812
Net cash used in investing activities	10,484	15,812
Cash flows used in financing activities:
Change in uncashed checks	0	0
Tax payments related to withholdings on vested restricted stock	0	0
Repurchases of common stock	0	0
Payments on finance lease	0
Principal payments on debt	0	0
Intercompany	(10,484)	(15,812)
Net cash used in financing activities	(10,484)	(15,812)
Effect of exchange rate change on cash	0	0
Decrease in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Clean Harbors, Inc. | Reportable Legal Entities
Condensed consolidating statement of cash flows
Net cash from operating activities	123	143
Cash flows used in investing activities:
Additions to property, plant and equipment	0	0
Proceeds from sale and disposal of fixed assets	0	0
Acquisitions, net of cash acquired	0	0
Additions to intangible assets including costs to obtain or renew permits	0	0
Proceeds from sale of available-for-sale securities	0
Purchases of available-for-sale securities	0
Proceeds from sale of available-for-sale securities		0
Purchases of available-for-sale securities		0
Intercompany	0	0
Net cash used in investing activities	0	0
Cash flows used in financing activities:
Change in uncashed checks	0	0
Tax payments related to withholdings on vested restricted stock	(2,276)	(548)
Repurchases of common stock	(6,324)	(14,264)
Payments on finance lease	0
Principal payments on debt	(1,884)	(1,000)
Intercompany	10,484	15,812
Net cash used in financing activities	0	0
Effect of exchange rate change on cash	0	0
Decrease in cash and cash equivalents	123	143
Cash and cash equivalents, beginning of period	27,308	51,638
Cash and cash equivalents, end of period	27,431	51,781
Guarantor Subsidiaries | Reportable Legal Entities
Condensed consolidating statement of cash flows
Net cash from operating activities	50,344	69,536
Cash flows used in investing activities:
Additions to property, plant and equipment	(48,696)	(37,319)
Proceeds from sale and disposal of fixed assets	3,366	292
Acquisitions, net of cash acquired	(14,870)	(120,000)
Additions to intangible assets including costs to obtain or renew permits	(1,294)	(1,234)
Proceeds from sale of available-for-sale securities	0
Purchases of available-for-sale securities	0
Proceeds from sale of available-for-sale securities		0
Purchases of available-for-sale securities		0
Intercompany	(10,484)	(15,812)
Net cash used in investing activities	(71,978)	(174,073)
Cash flows used in financing activities:
Change in uncashed checks	(4,454)	(3,578)
Tax payments related to withholdings on vested restricted stock	0	0
Repurchases of common stock	0	0
Payments on finance lease	(115)
Principal payments on debt	0	0
Intercompany	0	0
Net cash used in financing activities	(4,569)	(3,578)
Effect of exchange rate change on cash	0	0
Decrease in cash and cash equivalents	(26,203)	(108,115)
Cash and cash equivalents, beginning of period	101,302	207,777
Cash and cash equivalents, end of period	75,099	99,662
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed consolidating statement of cash flows
Net cash from operating activities	(20,727)	(17,776)
Cash flows used in investing activities:
Additions to property, plant and equipment	(10,251)	(6,923)
Proceeds from sale and disposal of fixed assets	955	506
Acquisitions, net of cash acquired	0	0
Additions to intangible assets including costs to obtain or renew permits	162	(11)
Proceeds from sale of available-for-sale securities	8,600
Purchases of available-for-sale securities	(12,941)
Proceeds from sale of available-for-sale securities		3,264
Purchases of available-for-sale securities		(3,003)
Intercompany	0	0
Net cash used in investing activities	(13,475)	(6,167)
Cash flows used in financing activities:
Change in uncashed checks	(315)	(265)
Tax payments related to withholdings on vested restricted stock	0	0
Repurchases of common stock	0	0
Payments on finance lease	0
Principal payments on debt	0	0
Intercompany	0	0
Net cash used in financing activities	(315)	(265)
Effect of exchange rate change on cash	1,461	(867)
Decrease in cash and cash equivalents	(33,056)	(25,075)
Cash and cash equivalents, beginning of period	97,897	59,984
Cash and cash equivalents, end of period	$ 64,841	$ 34,909