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Stockholders' Equity - Summary of Activity for PSUs awards (Detail) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Shares issued for SLO awards 71,893 101,062 51,321
Vested (172,071) (136,197) (98,550)
Restricted stock shares, forfeited (185,056)    
PSU Awards [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Non-vested at December 31, 2014 913,801    
Shares issued for SLO awards 224,760    
Vested (531,440)    
Restricted stock shares, forfeited (57,116)    
Non-vested at December 31, 2015 550,005 913,801  
Non-vested at December 31, 2014 $ 28.38    
Granted 50.11    
Vested 24.32    
Forfeited or expired 25.55    
Non-vested at December 31, 2015 $ 41.99 $ 28.38