CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues	$ 3,412,190	$ 3,300,303	$ 2,944,978
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	2,387,819	2,305,551	2,062,673
Selling, general and administrative expenses	484,054	503,747	456,648
Accretion of environmental liabilities	10,136	9,806	9,460
Depreciation and amortization	300,725	298,625	288,422
(Loss) income from operations	229,456	182,574	127,775
Other income (expense), net	2,897	(4,510)	(6,119)
Loss on early extinguishment of debt	(6,131)	(2,488)	(7,891)
Gain on sale of businesses	687	0	30,732
Interest expense, net of interest income of $4,227, $2,958 and $1,897, respectively	(78,670)	(81,094)	(85,808)
(Loss) income before (benefit) provision for income taxes	148,239	94,482	58,689
Provision (benefit) for income taxes	50,499	28,846	(42,050)
Net income	$ 97,740	$ 65,636	$ 100,739
Earnings per share:
Basic (in dollars per share)	$ 1.75	$ 1.17	$ 1.77
Diluted (in dollars per share)	$ 1.74	$ 1.16	$ 1.76
Shares used to compute earnings per share — Basic (in shares)	55,845	56,148	57,072
Shares used to compute earnings per share — Diluted (in shares)	56,129	56,340	57,200
Service revenues
Revenues:
Total revenues	$ 2,842,881	$ 2,709,239	$ 2,398,650
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	1,945,021	1,861,975	1,641,798
Product revenues
Revenues:
Total revenues	569,309	591,064	546,328
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 442,798	$ 443,576	$ 420,875