Stock Option Plan - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Available for Grant, Beginning balance	331,938,000
Options Available for Grant, Options granted	(102,462,000)
Options Available for Grant, Options forfeited	11,135,000
Options Available for Grant, Ending balance	240,611,000	331,938,000
Options Outstanding
Options Outstanding, Beginning balance	2,685,913,000
Options granted	102,462,000
Options exercised	(44,702,000)
Options forfeited	(11,135,000)
Options Outstanding, Ending balance	2,732,538,000	2,685,913,000
Options exercisable	1,794,651,000
Options vested and expected to vest	2,680,533,000
Options Outstanding, Weighted Average Exercise Price Per Share
Options Outstanding, Weighted Average Exercise Price Per Share, Beginning Balance	$ 4.81
Options Outstanding, Weighted Average Exercise Price Per Share, Options granted	10.31
Options Outstanding, Weighted Average Exercise Price Per Share, Options exercised	1.88
Options Outstanding, Weighted Average Exercise Price Per Share, Options forfeited	6.38
Options Outstanding, Weighted Average Exercise Price Per Share, Ending Balance	5.05	$ 4.81
Options Outstanding, Weighted Average Exercise Price Per Share, Exercisable	4.17
Options Outstanding, Weighted Average Exercise Price Per Share, vested and expected to vest	$ 5.01
Options Outstanding, Weighted- Average Remaining Contractual Life (years)	7 years 1 month 10 days	7 years 7 months 17 days
Options exercisable, Weighted- Average Remaining Contractual Life (years)	6 years 4 months 6 days
Options vested and expected to vest, Weighted- Average Remaining Contractual Life (years)	7 years 29 days
Options Outstanding, Aggregate Intrinsic Value	$ 21,880
Options exercisable, Aggregate Intrinsic Value	15,951
Options vested and expected to vest, Aggregate Intrinsic Value	$ 21,568