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Summary of Restricted Stock Unit Activity (Detail) - Restricted stock units - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Restricted stock units outstanding at December 31, 2014 1,013,683    
Granted 187,946    
Released (146,160)    
Forfeited (25,520)    
Restricted stock units outstanding at December 31, 2015 1,029,949 1,013,683  
Weighted average grant date fair value      
Restricted stock units outstanding at December 31, 2014 $ 44.34    
Granted 56.48 $ 48.56 $ 42.47
Released 40.96    
Forfeited 46.97    
Restricted stock units outstanding at December 31, 2015 $ 46.97 $ 44.34