Net Loss Per Share - Summary of Shares Excluded from Calculation of Diluted Loss Per Share with a Potential Dilutive Impact (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	4,282	19,055
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	3,261	3,910
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	17	103
Common Stock Subject to Repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	4	65
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact	1,000
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from calculation of diluted loss per share with a potential dilutive impact		14,977