CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenues	$ 175,884	$ 291,924	$ 507,977	$ 995,754
Cost of revenues (exclusive of items shown below)	146,615	234,640	434,868	768,702
Selling, general and administrative expenses	34,859	37,345	114,863	119,985
Depreciation and amortization	51,975	69,047	168,891	204,824
(Gain) loss on disposition of assets, net	(1,148)	3,791	(3,919)	1,115
Operating loss	(56,417)	(52,899)	(206,726)	(98,872)
Interest expense	(115)	(250)	(566)	(1,331)
Interest income	169	5	296	20
Other income (expense), net	86	(795)	274	4,932
Loss before income taxes	(56,277)	(53,939)	(206,722)	(95,251)
Income tax benefit	(17,335)	(18,766)	(86,583)	(33,571)
Net loss	$ (38,942)	$ (35,173)	$ (120,139)	$ (61,680)
Loss per share
Basic (in dollars per share)	$ (0.18)	$ (0.16)	$ (0.56)	$ (0.29)
Diluted (in dollars per share)	$ (0.18)	$ (0.16)	$ (0.56)	(0.29)
Dividends per share (in dollars per share)				$ 0.155