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Stockholders' Equity - Summary of Activity for Non-vested Three-year PSU awards (Detail) - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Shares issued for SLO Awards 20,587 71,893 101,062
Vested (179,826) (172,071) (136,197)
Restricted stock shares, forfeited (89,699) (185,056)  
PSU Awards [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Non-vested at December 31, 2015 550,005    
Shares issued for SLO Awards 290,146    
Vested (374,267)    
Restricted stock shares, forfeited (6,870)    
Non-vested at December 31, 2016 459,014 550,005  
Non-vested at December 31, 2015 $ 41.99    
Granted 49.14    
Vested 38.13    
Forfeited or expired 49.14    
Non-vested at December 31, 2016 $ 49.55 $ 41.99