Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Jun. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	5,902,480	4,766,580
Common Stock Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	25,970	25,970
Shares Available Under the 2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	984,357	984,357
Shares Available Under the 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	509,089	903,350
Shares Available Under the 2015 ESPP Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	433,845	227,623
Common Stock Options and Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	3,949,219	2,625,280