Earnings Per Share - Calculation of Basic and Diluted Weighted Average Shares Outstanding and Earnings Per Share (Detail) - USD ($) $ / shares in Units, 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
Basic:
Net income (loss)	$ (318,656)	$ (291,965)	$ (152,906)	$ (327,388)	$ (190,515)	$ (29,415)	$ 4,444	$ 25,943	$ (1,090,915)	$ (189,543)	$ 117,634
Net income attributable to participating securities									0	0	(2,817)
Net income (loss) attributable to common stock - basic									(1,090,915)	(189,543)	114,817
Diluted:
Net income (loss)	$ (318,656)	$ (291,965)	$ (152,906)	$ (327,388)	$ (190,515)	$ (29,415)	$ 4,444	$ 25,943	(1,090,915)	(189,543)	117,634
Net income attributable to participating securities									0	0	(2,815)
Net income (loss) attributable to common stock - diluted									$ (1,090,915)	$ (189,543)	$ 114,819
Weighted average shares (denominator):
Weighted average shares - basic (in shares)									55,250	52,721	48,693
Dilutive effect of stock options (in shares)									0	0	42
Weighted average shares - diluted (in shares)									55,250	52,721	48,735
Basic earnings (loss) per share (in usd per share)	$ (5.76)	$ (5.28)	$ (2.77)	$ (5.93)	$ (3.47)	$ (0.54)	$ 0.08	$ 0.52	$ (19.75)	$ (3.60)	$ 2.36
Diluted earnings (loss) per share (in usd per share)	$ (5.76)	$ (5.28)	$ (2.77)	$ (5.93)	$ (3.47)	$ (0.54)	$ 0.08	$ 0.52	$ (19.75)	$ (3.60)	$ 2.36