Share-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expected volatility term	5 years
Closing stock price	$ 116.07
Number of shares available for issuance	3,208,414
Equity Incentive Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Maximum aggregate number of shares that may be awarded and sold	7,543,321
Conversion ratio for awards granted	2
Conversion ratio for awards forfeited	2
Options granted under the 2006 Incentive Plan, expiration period	7 years
Options, exercisable period	4 years
Equity Incentive Plan | Restricted stock units | Lower Limit
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Vesting period	3 years
Equity Incentive Plan | Performance-based restricted stock | Lower Limit
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Vesting period	12 months
Employee Stock Purchase Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Maximum percentage of gross compensation that participating employees may annually contribute towards ESPP	10.00%
Maximum amount that participating employees may annually contribute towards ESPP	$ 25,000
Percentage of fair market value of common stock at which employees may purchase shares under ESPP	85.00%
Number of shares issued under ESPP	130,110
Proceeds from issuance of shares under ESPP	$ 11,900,000
Number of shares available for issuance	566,199