Common Stock - Summary of Common Stock Shares Activity (Detail) - shares			1 Months Ended	12 Months Ended
	Apr. 28, 2015	May. 07, 2014	May. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance (in shares)				8,512,103	334,068
Exercise of stock options (in shares)				0	416
Conversion of preferred stock (in shares)			1,691,884		1,691,884
Exercise of common stock warrants (in shares)		275,687	275,687		275,687
Common stock issued through IPO (in shares)	5,376,622	6,200,000		5,376,622	6,200,000
Common stock issued through employee stock purchase plan (in shares)				16,874	10,048
Ending Balance (in shares)				13,905,599	8,512,103