Fair Value Measurements - Reconciliation of Liabilities Measured at Fair Value Using Level 3 Significant Unobservable Inputs (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Balance, beginning of period	$ 2,460	$ 2,460
Reclassification of preferred stock warrant liability to additional paid-in capital upon conversion to common stock		(521)
Change in fair value of preferred stock warrant liabilities	$ (2,036)	$ (1,939)