Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Restricted Stock Award Activity (Detail)

v3.6.0.2
Share-Based Compensation - Restricted Stock Award Activity (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Intrinsic value of options vested and expected to vest $ 9.0    
Restricted Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Intrinsic value of options vested and expected to vest   $ 10.3 $ 6.0
Shares      
Unvested, beginning of period, Shares 535,208    
Granted, Shares 205,234    
Vested, Shares (212,811)    
Forfeited, Shares (21,242)    
Unvested, end of period, Shares 506,389    
Weighted Average Grant Date Fair Value      
Unvested, beginning of period, Weighted - average grant date fair value $ 24.87    
Granted, Weighted - average grant date fair value 44.22    
Vested, Weighted - average grant date fair value 19.75    
Forfeited, Weighted - average grant date fair value 26.69    
Unvested, end of period, Weighted - average grant date fair value $ 34.82    
Restricted Stock Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Intrinsic value of options vested and expected to vest $ 0.9 $ 0.9 $ 0.4