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Stockholders' Equity - Summary of Unvested Restricted Stock and Restricted Stock Unit (Detail) - USD ($)
$ / shares in Units, $ in Millions
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)    
Restricted Stock Shares [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Non-vested at December 31, 2014 1,561,969    
Shares issued for SLO awards 419,844    
Vested (593,970)    
Restricted stock shares, forfeited (118,068)    
Non-vested at December 31, 2015 1,269,775 1,561,969  
Number of non-vested restricted stock, Weighted- Average per Share Fair value on Grant Date, beginning of year $ 25.09    
Restricted stock for granted, Weighted- Average per Share Fair Value on Grant Date during the year 45.35    
Restricted stock vested/exercised, Weighted- Average per Share Fair Value on Grant Date during the year 17.21    
Restricted stock forfeited or expired, Weighted- Average per Share Fair Value on Grant Date during the year 29.57    
Number of non-vested restricted stock, Weighted- Average per Share Fair Value on Grant Date, Ending of year $ 35.09 $ 25.09  
Aggregate Intrinsic Value $ 28.8    
Restricted Stock Units [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Non-vested at December 31, 2014 791,335    
Shares issued for SLO awards 301,285    
Vested (172,071)    
Restricted stock shares, forfeited (38,100)    
Non-vested at December 31, 2015 882,449 791,335  
Number of non-vested restricted stock, Weighted- Average per Share Fair value on Grant Date, beginning of year $ 27.66    
Restricted stock for granted, Weighted- Average per Share Fair Value on Grant Date during the year 45.18    
Restricted stock vested/exercised, Weighted- Average per Share Fair Value on Grant Date during the year 17.62    
Restricted stock forfeited or expired, Weighted- Average per Share Fair Value on Grant Date during the year 20.16    
Number of non-vested restricted stock, Weighted- Average per Share Fair Value on Grant Date, Ending of year $ 35.93 $ 27.66  
Aggregate Intrinsic Value $ 8.5