Stock-Based Compensation - Summary of Share-Based Option Activity (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Outstanding, Begginning of Period	8,478,148
Shares Granted	545,812
Shares Exercised	(31,640)
Shares Canceled	(251,478)
Shares Outstanding, End of Period	8,740,842
Shares Vested and expected to vest at June 30, 2013	6,819,442
Shares Exercisable at June 30, 2013	1,362,327
Weighted Average Exercise Price Outstanding, Beginning of Period	$ 12.22
Weighted Average Exercise Price Granted	$ 13.64
Weighted Average Exercise Price Exercised	$ 8.22
Weighted Average Exercise Price Canceled	$ 12.46
Weighted Average Exercise Price Outstanding, End of Period	$ 12.32
Weighted Average Exercise Price Vested and expected to vest at June 30, 2013	$ 12.37
Weighted Average Exercise Price Exercisable at June 30, 2013	$ 11.69