Stock-Based Compensation - Company's Activities with Respect to its Stock Options (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares Outstanding, Beginning Balance	2,831
Number of Shares, Granted	964
Number of Shares, Exercised	(474)
Number of Shares, Canceled	(52)
Number of Shares Outstanding, Ending Balance	3,269
Number of Shares Exercisable, Ending Balance	1,480
Number of Shares Unvested, Ending Balance	1,789
Weighted-Average Exercise Price Per Share Outstanding, Beginning Balance	$ 34.06
Weighted-Average Exercise Price Per Share, Granted	$ 73.11
Weighted-Average Exercise Price Per Share, Exercised	$ 27.64
Weighted-Average Exercise Price Per Share, Canceled	$ 49.71
Weighted-Average Exercise Price Per Share Outstanding, Ending Balance	$ 46.25
Weighted-Average Exercise Price Per Share Exercisable, Ending Balance	$ 30.42
Weighted-Average Exercise Price Per Share Unvested, Ending Balance	$ 59.35
Weighted-Average Remaining Contractual Life (in Years) Outstanding at June 30, 2013	4 years 6 months 18 days
Weighted-Average Remaining Contractual Life (in years) Exercisable at June 30, 2013	2 years 10 months 6 days
Weighted-Average Remaining Contractual Life (in years) Unvested at June 30, 2013	5 years 11 months 12 days