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)