Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Reclassification to additional paid-in capital	$ (27,066)
Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance	100
Net increase in fair value upon remeasurement	1,108
Reclassification to additional paid-in capital	(1,208)
Common Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance	889
Net increase in fair value upon remeasurement	24,969
Reclassification to additional paid-in capital	$ (25,858)