Net Income (Loss) Per Share Attributable to Common Stockholders - Summary of Anti Dilutive Loss Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents excluded from the calculation of diluted net loss per share (in shares)	4,437,177	23,227,770	18,716,739
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents excluded from the calculation of diluted net loss per share (in shares)		20,454,489	16,761,805
Outstanding Stock Options and Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents excluded from the calculation of diluted net loss per share (in shares)	4,437,177	2,568,781	1,604,434
Common Stock Subject to Repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents excluded from the calculation of diluted net loss per share (in shares)		117,000	263,000
Preferred stock warrant
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents excluded from the calculation of diluted net loss per share (in shares)		87,500	87,500