UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Total revenues	$ 843,181	$ 755,846	$ 2,442,099	$ 2,197,575
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	580,685	519,595	1,710,694	1,535,983
Selling, general and administrative expenses	121,219	113,252	362,302	337,767
Accretion of environmental liabilities	2,450	2,347	7,328	7,053
Depreciation and amortization	73,082	72,989	220,686	216,932
Income from operations	65,745	47,663	141,089	99,840
Other expense, net	(996)	(432)	(449)	(2,814)
Loss on early extinguishment of debt	(2,469)	(1,846)	(2,469)	(7,891)
Loss on sale of business	0	(77)	0	31,645
Interest expense, net of interest income of $736, $573, $2,086 and $1,098, respectively	(19,916)	(20,675)	(60,955)	(65,743)
Income before (benefit) provision for income taxes	42,364	24,633	77,216	55,037
Provision for income taxes	11,275	12,575	28,011	38,492
Net income	$ 31,089	$ 12,058	$ 49,205	$ 16,545
Earnings per share:
Basic (in USD per share)	$ 0.55	$ 0.21	$ 0.88	$ 0.29
Diluted (in USD per share)	$ 0.55	$ 0.21	$ 0.87	$ 0.29
Shares used to compute loss per share - Basic (in shares)	56,059	57,033	56,222	57,149
Shares used to compute loss per share - Diluted (in shares)	56,291	57,195	56,360	57,280
Service
Revenues:
Total revenues	$ 685,183	$ 612,352	$ 2,001,681	$ 1,783,506
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	464,612	412,369	1,385,684	1,215,812
Product
Revenues:
Total revenues	157,998	143,494	440,418	414,069
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 116,073	$ 107,226	$ 325,010	$ 320,171