CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Revenues	$ 142,998	$ 297,560	$ 332,093	$ 703,830
Cost of revenues (exclusive of items shown below)	126,997	241,617	288,253	534,062
Selling, general and administrative expenses	36,458	40,208	80,004	82,640
Depreciation and amortization	56,280	69,801	116,916	135,777
Gain on disposition of assets, net	(1,515)	(1,718)	(2,771)	(2,676)
Operating loss	(75,222)	(52,348)	(150,309)	(45,973)
Interest expense	(126)	(390)	(451)	(1,081)
Interest income	104	9	127	15
Other (expense) income, net	(154)	143	188	5,727
Loss before income taxes	(75,398)	(52,586)	(150,445)	(41,312)
Income tax benefit	(26,712)	(18,531)	(69,248)	(14,805)
Net loss	$ (48,686)	$ (34,055)	$ (81,197)	$ (26,507)
Loss per share
Basic (in dollars per share)	$ (0.23)	$ (0.16)	$ (0.38)	$ (0.12)
Diluted (in dollars per share)	$ (0.23)	(0.16)	$ (0.38)	(0.12)
Dividends per share (in dollars per share)		$ 0.050		$ 0.155