CONSOLIDATED STATEMENTS OF (LOSS) INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Service revenues									$ 2,744,272	$ 2,639,796	$ 2,729,205
Product revenues									530,865	761,840	780,451
Total revenues	$ 713,044	$ 893,366	$ 936,228	$ 732,499	$ 845,024	$ 851,465	$ 858,480	$ 846,667	3,275,137	3,401,636	3,509,656
Cost of revenues: (exclusive of items shown separately below)
Service revenues									1,898,907	1,790,377	1,874,448
Product revenues									457,899	651,419	668,185
Total cost of revenues	522,965	634,646	652,688	546,507	610,720	598,407	606,950	625,719	2,356,806	2,441,796	2,542,633
Selling, general and administrative expenses									414,164	437,921	470,477
Accretion of environmental liabilities									10,402	10,612	11,541
Depreciation and amortization									274,194	276,083	264,449
Goodwill impairment charge									31,992	123,414	0
(Loss) income from operations	25,549	93,970	60,758	7,302	57,537	(42,748)	67,115	29,906	187,579	111,810	220,556
Other (expense) income	(990)	(139)	(660)	409	244	613	(655)	4,178	(1,380)	4,380	1,705
Interest expense, net of interest income of $626, $819, and $507, respectively									(76,553)	(77,668)	(78,376)
Income before provision for income taxes									109,646	38,522	143,885
Provision for income taxes									65,544	66,850	48,319
Net income (loss)	$ 568	$ 40,228	$ 10,395	$ (7,089)	$ 27,377	$ (93,337)	$ 28,672	$ 8,960	$ 44,102	$ (28,328)	$ 95,566
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.01	$ 0.69	$ 0.18	$ (0.12)	$ 0.46	$ (1.55)	$ 0.47	$ 0.15	$ 0.76	$ (0.47)	$ 1.58
Diluted (in dollars per share)	$ 0.01	$ 0.69	$ 0.18	$ (0.12)	$ 0.46	$ (1.55)	$ 0.47	$ 0.15	$ 0.76	$ (0.47)	$ 1.57
Shares used to compute earnings (loss) per share — Basic									58,324	60,311	60,574
Shares used to compute earnings (loss) per share — Diluted									58,434	60,311	60,728