Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Income Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share Basic And Diluted [Abstract]
Net income (loss) applicable to common stockholders	$ 151,093	$ (21,384)	$ 5,073	$ (957)	$ 7,697	$ 7,233	$ 2,066	$ (3,395)	$ 133,825	$ 13,601	$ (8,200)
Denominator:
Weighted average common shares outstanding, basic									87,401,123	85,882,646	85,051,066
Per share:
Net income (loss) per share applicable to common stockholders	$ 1.72	$ (0.24)	$ 0.06	$ (0.01)					$ 1.53	$ 0.16	$ (0.10)
Net income (loss) applicable to common stockholders	$ 151,093	$ (21,384)	$ 5,073	$ (957)	$ 7,697	$ 7,233	$ 2,066	$ (3,395)	$ 133,825	$ 13,601	$ (8,200)
Denominator:
Weighted average common shares outstanding									87,401,123	85,882,646	85,051,066
Dilutive securities:
Stock options									1,625,668	89,418
Restricted stock units									311,905	342,142
Diluted shares outstanding									89,338,696	86,314,206	85,051,066
Per share:
Net income (loss) per share applicable to common stockholders	$ 1.67	$ (0.24)	$ 0.06	$ (0.01)					$ 1.50	$ 0.16	$ (0.10)