Summary of Significant Accounting Policies - Summary of Earnings (Loss), Weighted Average Common Shares and Potential Common Shares Outstanding (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
Numerator:
Net income (loss) for basic and diluted (loss) earnings per share	$ (75,147)	$ (80,796)	$ 45,592	$ 39,476	$ 47,811	$ 96,431	$ 28,043	$ 64,487	$ (70,875)	$ 236,772	$ 19,396
Denominator:
Weighted average shares outstanding - basic									189,876	186,905	160,641
Dilutive effect of equity-based awards										4,545	3,372
Weighted average common shares outstanding - diluted									189,876	191,450	164,013
Earnings (loss) per share:
Basic	$ (0.39)	$ (0.42)	$ 0.24	$ 0.21	$ 0.25	$ 0.51	$ 0.15	$ 0.35	$ (0.37)	$ 1.27	$ 0.12
Diluted	$ (0.39)	$ (0.42)	$ 0.24	$ 0.20	$ 0.25	$ 0.50	$ 0.15	$ 0.34	$ (0.37)	$ 1.24	$ 0.12