Preferred Stock Warrant Liability - Summary of Rollforward of Fair Value of Preferred Stock Warrant Liability (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Beginning balance	$ 1,582,000	$ 164,000	$ 0
Loss from revaluation of preferred stock warrant liability	7,000	1,418,000	8,000
Reclassification to stockholders’ equity	(1,589,000)
Ending balance	0	1,582,000	164,000
Series A-2 Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Beginning balance	17,180	2,070
Issuance of Series A-2 preferred stock warrant			156,000
Ending balance	$ 17,260	$ 17,180	$ 2,070