Stock-based Compensation - Summary of Status of Company's Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items]
Number of Shares, Outstanding Beginning Balance	3,437,879
Number of Shares, Granted	56,570
Number of Shares, Exercised	(93,886)
Number of Shares, Canceled	(77,497)
Number of Shares, Outstanding Ending Balance	3,323,066
Number of Shares, Exercisable	2,481,977
Number of Shares, Vested or expected to vest	3,175,743
Exercise Price, Granted	$ 6.48
Weighted Average Exercise Price, Beginning Balance	$ 5.48
Weighted Average Exercise Price, Granted	$ 6.48
Weighted Average Exercise Price, Exercised	$ 1.15
Weighted Average Exercise Price, Canceled	$ 11.69
Weighted Average Exercise Price, Ending Balance	$ 5.47
Weighted Average Exercise Price, Exercisable	$ 3.58
Weighted Average Exercise Price, Vested and Expected to Vest	$ 5.19
Weighted Average Remaining Contractual Term, Ending Balance	6 years 7 months 2 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 7 days
Weighted Average Remaining Contractual Term, Vested and Expected to Vest	6 years 6 months
Aggregate Intrinsic Value, Exercised	$ 509
Aggregate Intrinsic Value, Ending Balance	8,790
Aggregate Intrinsic Value, Exercisable	8,689
Aggregate Intrinsic Value, Vested or Expected to Vest	$ 8,785
Minimum [Member]
Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items]
Exercise Price, Outstanding Beginning Balance	$ 0.31
Exercise Price , Exercised	$ 0.31
Exercise Price, Canceled	$ 1.72
Exercise Price, Outstanding Ending Balance	$ 0.31
Exercise Price, Exercisable	$ 0.31
Exercise Price, Vested or expected to vest	$ 0.31
Maximum [Member]
Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items]
Exercise Price, Outstanding Beginning Balance	$ 16.88
Exercise Price , Exercised	$ 9.31
Exercise Price, Canceled	$ 16.88
Exercise Price, Outstanding Ending Balance	$ 16.88
Exercise Price, Exercisable	$ 16.88
Exercise Price, Vested or expected to vest	$ 16.88