Share-Based Compensation - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Dec. 31, 2012
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expected volatility term			5 years
Closing stock price			55.97
Number of shares available for issuance			2,574,528
Equity Incentive Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Maximum aggregate number of shares that may be awarded and sold			3,000,000
Number of shares available for Grant additional shares approved in period	2,100,000	425,000
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			202,696
Proceeds from issuance of shares under ESPP			8,800,000
Number of shares available for issuance			872,725