Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Number of Options, Outstanding, Beginning balance	19,024
Number of Options, Granted	3
Number of Options, Exercised	(1,714)
Number of Options, Forfeited	(790)
Number of Options, Outstanding, Ending balance	16,523	19,024
Number of Options, Vested and expected to vest	16,367
Number of Options, Exercisable	13,827
Weighted-Average Exercise Price, Outstanding, Beginning balance	$ 5.77
Weighted-Average Exercise Price, Granted	4.00
Weighted-Average Exercise Price, Exercised	2.27
Weighted-Average Exercise Price, Forfeited	6.49
Weighted-Average Exercise Price, Outstanding, Ending balance	6.10	$ 5.77
Weighted-Average Exercise Price, Vested and expected to vest	6.10
Weighted-Average Exercise Price, Exercisable	$ 5.96
Weighted-Average Remaining Contractual Term	2 years 4 months 2 days	5 years 11 months 19 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	2 years 4 months 2 days
Weighted-Average Remaining Contractual Term, Exercisable	2 years 3 months
Aggregate Intrinsic Value, Outstanding	$ 1,989	$ 7,564
Aggregate Intrinsic Value, Vested and expected to vest	1,989
Aggregate Intrinsic Value, Exercisable	$ 1,989