Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at the beginning of the period (in shares)	18,066
Granted (in shares)	3,286
Exercised (in shares)	(913)
Cancelled (in shares)	(332)
Outstanding at the end of the period (in shares)	20,107	18,066
Number of shares vested and expected to vest	19,829
Number of stock option exercisable	15,672
Outstanding at the beginning of the period (in dollars per share)	$ 3.50
Granted (in dollars per share)	$ 6.04
Exercised (in dollars per share)	$ 2.23
Cancelled (in dollars per share)	$ 6.02
Outstanding at the end of the period (in dollars per share)	$ 3.93	$ 3.50
Weighted average exercise price of shares vested and expected to vest (in dollars per share)	$ 3.89
Weighted average exercise price for exercisable option (in dollars per share)	$ 3.19
Outstanding at the beginning of the period	6 years 1 month 10 days	6 years 6 months 15 days
Vested and expected to vest	6 years 26 days
Exercisable	5 years 3 months 29 days
Outstanding at the beginning of the period (in dollars)	$ 51,486
Outstanding at the end of the period (in dollars)	38,348	51,486
Shares vested and expected to vest (in dollars)	38,307
Options exercisable (in dollars)	$ 37,861