Share-Based Compensation Weighted Average Assumptions and Fair Values Used for Employee Stock Options and Restricted Stock Units (Detail) - Equity Incentive Plan - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Weighted average expected term of options in years	4 years 8 months 27 days	4 years 7 months 3 days	4 years 8 months 12 days
Weighted average expected volatility of the Company's underlying common stock	31.30%	35.90%	44.60%
Risk-free interest rate	1.49%	1.72%	0.70%
Expected dividend yield	$ 0	$ 0	$ 0
Weighted average grant date fair value-stock options (usd per share)	$ 37.86	$ 35.65	$ 27.28
Weighted average grant date fair value-restricted stock units (usd per share)	$ 129.23	$ 107.76	$ 71.57