Stock‑Based Compensation (Options) (Details) - Employee and non-employee stock options $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Stock Based Compensation
Shares available for grant, beginning balance	3,734
Additional shares authorized	2,014
Options granted (in shares)	(122)
Options forfeited (in shares)	384
Shares available for grant, end balance	6,010
Number of shares
Outstanding, beginning balance (in shares)	9,324
Options granted (in shares)	122
Options exercised (in shares)	(667)
Options forfeited (in shares)	(384)
Outstanding, end balance (in shares)	8,395
Exercisable (in shares)	5,241
Vested and expected to vest (in shares)	8,021
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per shares) | $ / shares	$ 3.96
Granted (in dollars per share) | $ / shares	7.79
Exercised (in dollars per share) | $ / shares	1.96
Forfeited (in dollars per share) | $ / shares	5.29
Outstanding, end balance (in dollars per shares) | $ / shares	4.11
Exercisable (in dollars per share) | $ / shares	2.12
Vested and expected to vest (in dollars per share) | $ / shares	$ 3.93
Additional disclosures
Weighted average contractual term, options outstanding	7 years 4 months 17 days
Exercisable (in years)	6 years 6 months
Vested and expected to vest (in years)	7 years 3 months 22 days
Aggregate intrinsic value, options outstanding | $	$ 48,499
Aggregate intrinsic value, options exercisable | $	38,941
Aggregate intrinsic value, vested and expected to vest | $	$ 47,533