Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Annual Activity of Stock Option Plans [Line Items]
Outstanding, Shares	3,559
Granted, Shares	783
Exercised, Shares	(397)
Forfeited or expired, Shares	(88)
Outstanding, Shares	3,857
Exercisable, Shares	1,383
Options vested or expected to vest	3,386
Outstanding, Weighted-Average Exercise Price	$ 25.56
Granted, Weighted-Average Exercise Price	$ 42.11
Exercised, Weighted-Average Exercise Price	$ 23.10
Forfeited or expired, Weighted-Average Exercise Price	$ 31.79
Outstanding, Weighted-Average Exercise Price	$ 29.04
Exercisable, Weighted-Average Exercise Price	$ 23.26
Options vested or expected to vest, Weighted-Average Exercise Price	$ 28.22
Outstanding, Weighted-Average Remaining Contractual Term (in years)	7 years 6 months
Exercisable, Weighted-Average Remaining Contractual Term (in years)	5 years 10 months 24 days
Options vested or expected to vest, Weighted-Average Remaining Contractual Term (in years)	7 years 3 months 18 days
Outstanding, Aggregate Intrinsic Value	$ 50,634
Exercisable, Aggregate Intrinsic Value	26,174
Options vested or expected to vest, Aggregate Intrinsic Value	$ 47,243