REVENUES (Tables)

9 Months Ended

Sep. 30, 2022

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

The following tables present the Company's third-party revenue disaggregated by source of revenue and geography (in thousands):

	For the Three Months Ended September 30, 2022
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	960,737	$	249,035	$	283	$	1,210,055
Canada	119,295		33,736		—		153,031
Total third-party revenues	$	1,080,032	$	282,771	$	283	$	1,363,086
Sources of Revenue
Technical Services	$	398,664	$	—	$	—	$	398,664
Field and Emergency Response Services	150,031		—		—		150,031
Industrial Services and Other	332,025		—		283		332,308
Safety-Kleen Environmental Services	199,312		52,072		—		251,384
Safety-Kleen Oil	—		230,699		—		230,699
Total third-party revenues	$	1,080,032	$	282,771	$	283	$	1,363,086

	For the Three Months Ended September 30, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	632,755	$	185,096	$	59	$	817,910
Canada	111,076		22,493		—		133,569
Total third-party revenues	$	743,831	$	207,589	$	59	$	951,479
Sources of Revenue
Technical Services	$	308,158	$	—	$	—	$	308,158
Field and Emergency Response Services	116,677		—		—		116,677
Industrial Services and Other	154,977		—		59		155,036
Safety-Kleen Environmental Services	164,019		39,551		—		203,570
Safety-Kleen Oil	—		168,038		—		168,038
Total third-party revenues	$	743,831	$	207,589	$	59	$	951,479

	For the Nine Months Ended September 30, 2022
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	2,740,994	$	688,444	$	434	$	3,429,872
Canada	364,342		94,293		—		458,635
Total third-party revenues	$	3,105,336	$	782,737	$	434	$	3,888,507
Sources of Revenue
Technical Services	$	1,109,339	$	—	$	—	$	1,109,339
Field and Emergency Response Services	427,250		—		—		427,250
Industrial Services and Other	1,001,733		—		434		1,002,167
Safety-Kleen Environmental Services	567,014		145,841		—		712,855
Safety-Kleen Oil	—		636,896		—		636,896
Total third-party revenues	$	3,105,336	$	782,737	$	434	$	3,888,507

	For the Nine Months Ended September 30, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	1,824,848	$	504,302	$	217	$	2,329,367
Canada	295,008		61,710		—		356,718
Total third-party revenues	$	2,119,856	$	566,012	$	217	$	2,686,085
Sources of Revenue
Technical Services	$	887,063	$	—	$	—	$	887,063
Field and Emergency Response Services	328,831		—		—		328,831
Industrial Services and Other	425,154		—		217		425,371
Safety-Kleen Environmental Services	478,808		118,982		—		597,790
Safety-Kleen Oil	—		447,030		—		447,030
Total third-party revenues	$	2,119,856	$	566,012	$	217	$	2,686,085

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

Schedule of Contract Balances

(in thousands)	September 30, 2022		December 31, 2021
Receivables	$	1,026,226	$	792,734
Contract assets (unbilled receivables)	134,742		94,963
Contract liabilities (deferred revenue)	93,425		83,749