CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Revenues	$ 297,560	$ 582,831	$ 703,830	$ 1,084,523
Cost of revenues (exclusive of items shown below)	241,617	374,275	534,062	704,290
Selling, general and administrative expenses	40,397	47,603	83,034	96,311
Depreciation and amortization	69,801	56,517	135,777	112,022
(Gain) loss on disposition of assets, net	(1,718)	1,405	(2,676)	3,637
Operating (loss) profit	(52,537)	103,031	(46,367)	168,263
Interest expense	(390)	(49)	(1,081)	(386)
Interest income	9	6	15	10
Other income, net	332	831	6,121	911
(Loss) income before income taxes	(52,586)	103,819	(41,312)	168,798
Income tax (benefit) provision	(18,531)	40,536	(14,805)	66,127
Net (loss) income	$ (34,055)	$ 63,283	$ (26,507)	$ 102,671
(Loss) earnings per share
Basic (in dollars per share)	$ (0.16)	$ 0.29	$ (0.12)	$ 0.48
Diluted (in dollars per share)	(0.16)	0.29	(0.12)	0.47
Dividends per share (in dollars per share)	$ 0.050	$ 0.105	$ 0.155	$ 0.210
Weighted average shares outstanding
Basic (in shares)	212,598	215,224	213,586	215,199
Diluted (in shares)	212,598	216,238	213,586	216,280