Share-Based Compensation Stock Option Information Related to Equity Incentive Plan (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Options
Outstanding, beginning of period (in shares) | shares	1,394,888
Granted (in shares) | shares	123,561
Exercised (in shares) | shares	(357,441)
Forfeited (in shares) | shares	(22,260)
Expired (in shares) | shares	(1,520)
Outstanding, end of period (in shares) | shares	1,137,228
Vested and expected to vest (in shares) | shares	1,107,168
Exercisable (in shares) | shares	613,873
Weighted average exercise price
Outstanding, beginning of period (usd per share) | $ / shares	$ 66.03
Granted (usd per share) | $ / shares	129.20
Exercised (usd per share) | $ / shares	51.52
Forfeited (usd per share) | $ / shares	84.17
Expired (usd per share) | $ / shares	48.76
Outstanding, end of period (usd per share) | $ / shares	77.12
Vested and expected to vest (usd per share) | $ / shares	76.33
Exercisable (usd per share) | $ / shares	$ 60.86
Weighted Average Remaining Contractual Life in Years
Outstanding (in years)	3 years 9 months 23 days
Vested and expected to vest (in years)	3 years 9 months 7 days
Exercisable (in years)	2 years 9 months 19 days
Aggregate Intrinsic Value of In-The-Money Options
Outstanding | $	$ 48,803,591
Vested and expected to vest | $	48,309,612
Exercisable | $	$ 35,630,862