Stock-Based Compensation - Stock Options (Details) - Employee and non-employee stock options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Based Compensation
Shares available for grant, beginning balance	3,743
Additional shares authorized	2,014
Options granted (in shares)	(2,558)
Options forfeited (in shares)	916
Shares available for grant, end balance	4,115	3,743
Number of shares
Outstanding, beginning balance (in shares)	9,316
Options granted (in shares)	2,558
Options exercised (in shares)	(1,915)
Options forfeited (in shares)	(916)
Outstanding, end balance (in shares)	9,043	9,316
Exercisable (in shares)	5,054
Vested and expected to vest (in shares)	9,039
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 3.96
Granted (in dollars per share)	10.23
Exercised (in dollars per share)	1.88
Forfeited (in dollars per share)	8.28
Outstanding, end balance (in dollars per share)	5.72	$ 3.96
Exercisable (in dollars per share)	3.10
Vested and expected to vest (in dollars per share)	$ 5.72
Additional disclosures
Weighted average contractual term, options outstanding	7 years 6 months 18 days	8 years 3 months 22 days
Exercisable (in years)	6 years 6 months 4 days
Vested and expected to vest (in years)	7 years 6 months 18 days
Aggregate intrinsic value, options outstanding	$ 55,396	$ 63,713
Aggregate intrinsic value, options exercisable	43,938
Aggregate intrinsic value, vested and expected to vest	55,386
Aggregate intrinsic value, options exercised	16,900	6,900	$ 1,200
Fair value, options vested	$ 8,500	$ 4,500	$ 4,100
Weighted-average grant date fair value, options granted	$ 5.92	$ 7.29	$ 3.28