Share-Based Compensation - Share-Based Payment Award Activity (Detail)	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Options
Outstanding, beginning of period | shares	1,137,228
Exercised | shares	(31,006)
Forfeited | shares	(4,154)
Outstanding, end of period | shares	1,102,068
Vested and expected to vest, end of period | shares	1,078,583
Exercisable, end of period | shares	589,043
Weighted Average Exercise Price
Outstanding, beginning of period | $ / shares	$ 77.12
Exercised | $ / shares	25.17
Forfeited | $ / shares	87.99
Outstanding, end of period | $ / shares	78.54
Vested and expected to vest, end of period | $ / shares	77.88
Exercisable, end of period | $ / shares	$ 63.10
Weighted Average Remaining Contractual Life - in Years
Outstanding, end of period	3 years 7 months 24 days
Vested and expected to vest, end of period	3 years 7 months 10 days
Exercisable, end of period	2 years 8 months 5 days
Aggregate Intrinsic Value of In-The-Money Options
Outstanding, end of period | $	$ 30,595,989
Vested and expected to vest, end of period | $	30,455,095
Exercisable, end of period | $	$ 23,310,253