REVENUES (Tables)

3 Months Ended

Mar. 31, 2018

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table presents our revenues disaggregated by revenue source (in thousands):

	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
	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
Kleen Performance Products	—		115,757		—		115,757
Total third party revenues	$	439,688	$	309,918	$	172	$	749,778

	Three Months Ended March 31, 2017
	Environmental Services		Safety-Kleen		Corporate		Total
Primary Geographical Markets
United States	$	313,783	$	272,071	$	133	$	585,987
Canada	82,124		20,830		—		102,954
	395,907		292,901		133		688,941
Sources of Revenue (1)
Technical Services	230,218		—		—		230,218
Field and Emergency Response Services	61,019		—		—		61,019
Industrial Services	75,068		—		—		75,068
Oil, Gas and Lodging Services and Other	29,602		—		133		29,735
Safety-Kleen Environmental Services	—		191,727		—		191,727
Kleen Performance Products	—		101,174		—		101,174
Total third party revenues	$	395,907	$	292,901	$	133	$	688,941

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1. All revenue except Kleen Performance Products and product sales within Safety-Kleen Environmental Services, including allied products and direct blended oil sales, are recognized over time. Kleen Performance Products and Safety-Kleen Environmental Services product revenues are recognized at a point in time.

Contract Balances

Contract Balances

	March 31, 2018		December 31, 2017		March 31, 2017		December 31, 2016
Receivables	$	551,841	$	528,924	$	480,044	$	496,226
Contract Assets	63,375		35,922		28,106		36,190
Contract Liabilities	68,748		67,822		64,379		64,397