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Share-Based Compensation - Information for Restricted Stock Units under Equity Incentive Plan (Detail) - Restricted stock units
3 Months Ended
Mar. 31, 2017
$ / shares
shares
Shares  
Nonvested, beginning of period, in shares | shares 670,969
Granted, in shares | shares 54,240
Vested, in shares | shares (36,414)
Forfeited, in shares | shares (9,263)
Nonvested, end of period, in shares | shares 679,532
Weighted Average Grant Date Fair Value  
Nonvested, beginning of period, in usd per share | $ / shares $ 106.64
Granted, in usd per share | $ / shares 185.72
Vested, in usd per share | $ / shares 105.65
Forfeited, in usd per share | $ / shares 107.70
Nonvested, end of period, in usd per share | $ / shares $ 112.99