Stock Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance	1,800,000
Shares of common stock available for issuance	530,857
Contractual life in years		6 years 6 months
Vesting period of stock options in years	3 years
The weighted-average grant-date fair value of options granted		$ 27.56	$ 12.14
The weighted-average remaining contractual term for options outstanding	5 years 9 months 18 days	6 years 4 months 24 days
The weighted-average remaining contractual term for options vested and exercisable	5 years 6 months
The weighted-average remaining contractual term for options expected to vest	7 years 8 months 12 days
Aggregate intrinsic value of options outstanding	$ 22,200,000
Aggregate intrinsic value of options vested and exercisable	20,100,000
Aggregate intrinsic value of options expected to vest	1,900,000
The total grant-date fair value of options vested	1,200,000	100,000	500,000
The total intrinsic value of options exercised	9,200,000	900,000	100,000
Cash received from stock option exercises	2,636,000	1,345,000	146,000
Grant-date intrinsic value of RSU	$ 8,400,000
Weighted average remaining contractual life	1 year 4 months 24 days
Weighted-average grant-date fair value	$ 81.47	$ 52.28	$ 20.21
The total grant-date fair value of options vested	30,700,000	2,900,000	1,500,000
Cash used for employee withholding tax payments	11,500,000	700,000	400,000
Share settlement under RSUs	143,102	12,484	18,122
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized stock-based compensation expense	7,100,000	7,100,000
weighted average remaining amortization periods	1.4	0.9
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life in years	1 year
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life in years	3 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life in years	10 years
Unamortized stock-based compensation expense	200,000	500,000
weighted average remaining amortization periods	0.7	0.5
Rsu And Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company granted performance contingent RSU	47,996	88,030	0
Stock-based compensation expense	1,700,000	1,300,000
Unamortized stock-based compensation expense	$ 3,200,000	$ 3,000,000