XML 59 R49.htm IDEA: XBRL DOCUMENT v3.8.0.1
Share-Based Compensation - Information for Restricted Stock Units under Equity Incentive Plan (Detail) - Restricted stock units
3 Months Ended
Mar. 31, 2018
$ / shares
shares
Shares  
Nonvested, beginning of period, in shares | shares 637,667
Granted, in shares | shares 10,699
Vested, in shares | shares (42,171)
Forfeited, in shares | shares (13,332)
Nonvested, end of period, in shares | shares 592,863
Weighted Average Grant Date Fair Value  
Nonvested, beginning of period, in usd per share | $ / shares $ 135.86
Granted, in usd per share | $ / shares 237.94
Vested, in usd per share | $ / shares 126.23
Forfeited, in usd per share | $ / shares 132.87
Nonvested, end of period, in usd per share | $ / shares $ 138.46