UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues:
Service revenues	$ 610,940	$ 584,562	$ 1,171,154	$ 1,114,793
Product revenues	141,848	112,948	270,575	218,800
Total revenues	752,788	697,510	1,441,729	1,333,593
Cost of revenues (exclusive of items shown separately below)
Service revenues	412,356	388,684	803,443	762,670
Product revenues	107,447	91,318	212,945	181,611
Total cost of revenues	519,803	480,002	1,016,388	944,281
Selling, general and administrative expenses	112,294	107,063	224,515	211,547
Accretion of environmental liabilities	2,416	2,548	4,706	5,053
Depreciation and amortization	71,531	73,393	143,943	142,295
Income from operations	46,744	34,504	52,177	30,417
Other expense	(833)	(189)	(2,382)	(539)
Loss on early extinguishment of debt	(6,045)	0	(6,045)	0
Gain on sale of business	31,722	0	31,722	0
Interest expense, net of interest income of $311, $225, $520 and $375, respectively	(22,492)	(21,647)	(45,068)	(40,627)
Income (loss) before (benefit) provision for income taxes	49,096	12,668	30,404	(10,749)
Provision for income taxes	23,216	8,702	25,917	6,156
Net income (loss)	$ 25,880	$ 3,966	$ 4,487	$ (16,905)
Earnings (loss) per share:
Basic (in USD per share)	$ 0.45	$ 0.07	$ 0.08	$ (0.29)
Diluted (in USD per share)	$ 0.45	$ 0.07	$ 0.08	$ (0.29)
Shares used to compute loss per share - Basic (in shares)	57,190	57,549	57,226	57,599
Shares used to compute loss per share - Diluted (in shares)	57,336	57,678	57,349	57,599