Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Year
Number of Options
Outstanding at January 1, 2011	6,160,893
Granted	522,870
Exercised	(865,396)
Canceled	(146,709)
Outstanding at December 31, 2011	5,671,658
Vested and expected to vest at December 31, 2011	5,405,693
Options Exercisable at December 31, 2011	3,209,850
Weighted-Average Exercise Price
Outstanding at January 1, 2011	$ 28.14
Granted	$ 45.66
Exercised	$ 22.37
Canceled	$ 28.64
Outstanding at December 31, 2011	$ 30.62
Vested and expected to vest at December 31, 2011	$ 30.73
Options Exercisable at December 31, 2011	$ 35.12
Weighted-Average Remaining Contractual Term
Outstanding at January 1, 2011	6.62
Outstanding at December 31, 2011	6.15
Vested and expected to vest at December 31, 2011	6.06
Options Exercisable at December 31, 2011	4.96
Aggregate Intrinsic Value
Outstanding at January 1, 2011	$ 118,283	[1]
Outstanding at December 31, 2011	21,887	[1]
Vested and expected to vest at December 31, 2011	20,812	[1]
Options Exercisable at December 31, 2011	$ 7,349	[1]

[1] The intrinsic value represents the amount by which the fair value of stock exceeds the option exercise price as of December 31, 2011.