Fair Value of Financial Measurements - Schedule of Change in Company's Level 3 Liabilities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Convertible Preferred Stock Warrant Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Beginning Balance	$ 482
Change in fair value	(267)
Reclassification to stockholders' equity	(215)
Convertible Notes Redemption Rights Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Beginning Balance	480
Change in fair value	(480)
2020 Convertible Notes Derivative Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Change in fair value	42,793
Conversion to common stock	(55,216)
2020 Convertible Notes Derivative Liability [Member] | 2020 Convertible Notes [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Issuance of Notes	$ 12,423