Common Stock and Stockholders' Equity - Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Number of options
Number of options (in shares), outstanding at December 31, 2014 | shares	6,643,000
Number of options, Granted (in shares) | shares	1,915,000
Number of options, Exercised (in shares) | shares	(2,299,000)
Number of options, Canceled/forfeited/expired (in shares) | shares	(1,133,000)
Number of options (in shares), outstanding at September 30, 2015 | shares	5,125,667
Number of options, Vested or expected to vest at December 31, 2015 (in shares) | shares	4,911,000
Number of options, Exercisable at December 31, 2015 (in shares) | shares	1,963,000
Weighted average exercise price
Weighted average exercise price, Options outstanding at December 31, 2014 (in dollars per share) | $ / shares	$ 6.95
Weighted average exercise price, Granted (in dollars per share) | $ / shares	10.98
Weighted average exercise price, Exercised (in dollars per share) | $ / shares	2.95
Weighted average exercise price, Canceled/forfeited/expired (in dollars per share) | $ / shares	13.13
Weighted average exercise price, Options outstanding at December 31, 2015 (in dollars per share) | $ / shares	8.91
Weighted average exercise price, Vested or expected to vest at December 31, 2015 (in dollars per share) | $ / shares	8.83
Weighted average exercise price, Exercisable at December 31, 2015 (in dollars per share) | $ / shares	$ 6.37
Weighted average remaining contractual term
Weighted average remaining contractual term, Options outstanding at December 31, 2015	7 years 7 months 6 days
Weighted average remaining contractual term, Vested or expected to vest at December 31, 2015	7 years 7 months 6 days
Weighted average remaining contractual term, Exercisable at December 31, 2015	5 years 3 months 18 days
Aggregate intrinsic value
Aggregate intrinsic value, Options outstanding at December 31, 2015 | $	$ 8,461
Aggregate intrinsic value, Vested or expected to vest at December 31, 2015 | $	8,319
Aggregate intrinsic value, Exercisable at December 31, 2015 | $	$ 5,816