REVENUES (Tables)

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

We disaggregate the Company's third party revenues by geographic location and source of revenue as we believe these categories depict how revenue and cash flows are affected by economic factors (in thousands):

	For the Three Months Ended March 31, 2020
	Environmental Services		Safety-Kleen		Corporate			Total
Primary Geographical Markets
United States	$	440,014	$	306,533	$	(302	)	$	746,245
Canada	88,090		23,836		392			112,318
Total third-party revenues	$	528,104	$	330,369	$	90		$	858,563
Sources of Revenue (1)
Technical Services	$	275,273	$	—	$	—		$	275,273
Field and Emergency Response Services	105,912		—		—			105,912
Industrial Services and Other	146,919		—		90			147,009
Safety-Kleen Environmental Services	—		214,481		—			214,481
Safety-Kleen Oil	—		115,888		—			115,888
Total third-party revenues	$	528,104	$	330,369	$	90		$	858,563

	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 and Other (2)	150,153		—		594		150,747
Safety-Kleen Environmental Services	—		207,083		—		207,083
Safety-Kleen Oil	—		99,464		—		99,464
Total third-party revenues	$	473,698	$	306,547	$	594	$	780,839

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

(2) Third-party revenues of $34,055 and $594, respectively, previously reported as Oil, Gas and Lodging Services and Other for the three months ended March 31, 2019 are now disclosed within Industrial Services and Other based on relative materiality to the business.

Contract Balances

(in thousands)	March 31, 2020		December 31, 2019
Receivables	$	658,482	$	644,738
Contract assets (unbilled receivables)	51,215		56,326
Contract liabilities (deferred revenue)	71,243		73,370