Stock-Based Compensation - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unvested options
Period of time, from termination date, that unvested shares issued to an employee from early exercise of stock options can be repurchased by the Company	90 days
Unvested options exercised (in shares)	0	337	55,908
Unvested shares subject to repurchase right (in shares)	977	16,682
Liability related to share-based compensation	$ 4,000	$ 67,000
Employee stock options
Weighted Average Exercise Price
Granted (in dollars per share)	$ 21.24	$ 17.79	$ 7.13
2001 Stock Plan, 2011 Stock Plan and 2015 Stock Plan
Number of Shares Underlying Options
Outstanding at beginning of period (in shares)	5,701,000	5,657,000	4,472,000
Granted (in shares)	1,979,000	1,139,000	1,571,000
Exercised (in shares)	(1,660,000)	(1,022,000)	(348,000)
Canceled/forfeited/expired (in shares)	(109,000)	(73,000)	(38,000)
Outstanding at end of period (in shares)	5,911,000	5,701,000	5,657,000	4,472,000
Vested and expected to vest at end of period (in shares)	5,791,000
Exercisable at end of period (in shares)	2,977,000
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 7.10	$ 3.93	$ 2.65
Granted (in dollars per share)	21.24	18.07	7.13
Exercised (in dollars per share)	3.65	1.70	1.98
Canceled/forfeited/expired (in dollars per share)	20.00	6.56	4.85
Outstanding at end of period (in dollars per share)	12.57	$ 7.10	$ 3.93	$ 2.65
Vested and expected to vest at end of period (in dollars per share)	12.44
Exercisable at end of period (in dollars per share)	$ 6.20
Additional disclosures
Weighted Average Remaining Contractual Life	7 years 3 months 18 days	6 years 8 months 12 days	6 years 3 months 18 days	6 years 2 months 12 days
Outstanding, Aggregate Intrinsic Value	$ 129,591,000	$ 102,390,000	$ 16,131,000	$ 9,299,000
Exercised, Aggregate Intrinsic Value	42,458,000	$ 9,174,000	$ 1,249,000
Vested and expected to vest, Aggregate Intrinsic Value	127,711,000
Exercisable, Aggregate Intrinsic Value	$ 83,636,000