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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic:
Net income (loss)	$ (152,906)	$ 4,444	$ (480,294)	$ 30,387
Net income attributable to participating securities		(111)		(698)
Net income (loss) attributable to common stock - basic	(152,906)	4,333	(480,294)	29,689
Diluted:
Net income (loss)	(152,906)	4,444	(480,294)	30,387
Net income attributable to participating securities		(111)		(697)
Net income (loss) attributable to common stock - diluted	$ (152,906)	$ 4,333	$ (480,294)	$ 29,690
Weighted average shares (denominator):
Weighted average shares - basic	55,251	52,050	55,216	50,540
Dilutive effect of stock options		58		54
Dilutive effect of convertible notes		265		133
Weighted average shares - diluted	55,251	52,373	55,216	50,727
Basic earnings (loss) per share	$ (2.77)	$ 0.08	$ (8.70)	$ 0.59
Diluted earnings (loss) per share	$ (2.77)	$ 0.08	$ (8.70)	$ 0.59