Share-Based Compensation - Share-Based Payment Award Activity (Detail)	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Options
Outstanding, beginning of period, in shares | shares	1,010,557.000
Exercised, in shares | shares	(140,698)
Forfeited, in shares | shares	(1,605)
Outstanding, end of period, in shares | shares	868,254
Vested and expected to vest, end of period, in shares | shares	848,536
Exercisable, end of period, in shares | shares	442,135
Weighted Average Exercise Price
Outstanding, beginning of period, in usd per share | $ / shares	$ 87.24
Exercised, in usd per share | $ / shares	65.76
Forfeited, in usd per share | $ / shares	93.18
Outstanding, end of period, in usd per share | $ / shares	90.71
Vested and expected to vest, end of period, in usd per share | $ / shares	90.25
Exercisable, end of period, in usd per share | $ / shares	$ 76.45
Weighted Average Remaining Contractual Life - in Years
Outstanding, end of period	3 years 9 months 18 days
Vested and expected to vest, end of period	3 years 9 months 4 days
Exercisable, end of period	2 years 8 months 9 days
Aggregate Intrinsic Value of In-The-Money Options
Outstanding, end of period | $	$ 82,818,255
Vested and expected to vest, end of period | $	81,319,775
Exercisable, end of period | $	$ 48,474,704