UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 891,668	$ 843,181	$ 2,541,185	$ 2,442,099
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	612,754	580,685	1,772,051	1,710,694
Selling, general and administrative expenses	122,301	121,219	361,033	362,302
Accretion of environmental liabilities	2,490	2,450	7,624	7,328
Depreciation and amortization	73,756	73,082	223,328	220,686
Income from operations	80,367	65,745	177,149	141,089
Other (expense) income, net	(427)	(996)	1,992	(449)
Loss on early extinguishment of debt	(6,119)	(2,469)	(6,119)	(2,469)
Interest expense, net of interest income of $1,152, $736, $2,981 and $2,086, respectively	(19,702)	(19,916)	(59,681)	(60,955)
Income before provision for income taxes	54,119	42,364	113,341	77,216
Provision for income taxes	17,750	11,275	39,752	28,011
Net income	$ 36,369	$ 31,089	$ 73,589	$ 49,205
Earnings per share:
Basic (in USD per share)	$ 0.65	$ 0.55	$ 1.32	$ 0.88
Diluted (in USD per share)	$ 0.65	$ 0.55	$ 1.31	$ 0.87
Shares used to compute earnings per share - Basic (in shares)	55,850	56,059	55,858	56,222
Shares used to compute earnings per share - Diluted (in shares)	56,165	56,291	56,109	56,360
Service
Revenues:
Total revenues	$ 739,919	$ 685,183	$ 2,111,662	$ 2,001,681
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	496,005	464,612	1,439,717	1,385,684
Product
Revenues:
Total revenues	151,749	157,998	429,523	440,418
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 116,749	$ 116,073	$ 332,334	$ 325,010