CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Total revenues	$ 3,805,566	$ 3,144,097	$ 3,412,190
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	2,609,837	2,137,751	2,387,819
Selling, general and administrative expenses	537,962	451,044	484,054
Accretion of environmental liabilities	11,745	11,051	10,136
Depreciation and amortization	298,135	292,915	300,725
Income from operations	347,887	251,336	229,456
Other (expense) income, net	(515)	(290)	2,897
Loss on early extinguishment of debt	0	0	(6,131)
(Loss) gain on sale of businesses	0	(3,376)	687
Interest expense, net of interest income of $2,218, $3,462 and $4,227, respectively	(77,657)	(73,120)	(78,670)
Income from operations before provision for income taxes	269,715	174,550	148,239
Provision for income taxes	66,468	39,713	50,499
Net income	$ 203,247	$ 134,837	$ 97,740
Earnings per share:
Basic (in dollars per share)	$ 3.73	$ 2.43	$ 1.75
Diluted (in dollars per share)	$ 3.71	$ 2.42	$ 1.74
Shares used to compute earnings per share — Basic (in shares)	54,514	55,479	55,845
Shares used to compute earnings per share — Diluted (in shares)	54,761	55,690	56,129
Service revenues
Revenues:
Total revenues	$ 3,048,019	$ 2,724,584	$ 2,842,881
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	2,105,043	1,786,718	1,945,021
Product revenues
Revenues:
Total revenues	757,547	419,513	569,309
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 504,794	$ 351,033	$ 442,798