Stock-Based Compensation Expense - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Annual Activity of Stock Option Plans [Line Items]
Outstanding, Shares	4,473
Granted	53
Exercised	(842)
Forfeited or expired	(125)
Outstanding, Shares	3,559
Exercisable, Shares	1,186
Options vested or expected to vest	3,203
Outstanding, Weighted-Average Exercise Price	$ 24.48
Granted, Weighted-Average Exercise Price	$ 36.60
Exercised, Weighted-Average Exercise Price	$ 20.72
Forfeited or expired, Weighted-Average Exercise Price	$ 24.11
Outstanding, Weighted-Average Exercise Price	$ 25.56
Exercisable, Weighted-Average Exercise Price	$ 21.37
Options vested or expected to vest, Weighted-Average Exercise Price	$ 25.15
Outstanding, Weighted-Average Remaining Contractual Term (in years)	7 years 1 month 6 days
Exercisable, Weighted-Average Remaining Contractual Term (in years)	5 years 4 months 24 days
Options vested or expected to vest, Weighted-Average Remaining Contractual Term (in years)	6 years 10 months 24 days
Outstanding, Aggregate Intrinsic Value	$ 40,098
Exercisable, Aggregate Intrinsic Value	18,351
Options vested or expected to vest, Aggregate Intrinsic Value	$ 37,424