Stockholder's Equity - Schedule of Reserved Shares of Common Stock for Future Issuance (Detail) - shares	Jun. 30, 2016	Jan. 01, 2016	Dec. 31, 2015	Jan. 01, 2015
Class of Stock [Line Items]
Outstanding stock options (in shares)	1,804,473		1,379,727
Outstanding Series C-1 Preferred warrants (in shares)	14,033		14,033
Total common shares reserved for future issuance (in shares)	6,964,613		2,161,458
2014 Equity Incentive Plan [Member]
Class of Stock [Line Items]
Possible future issuance under equity compensation plan (in shares)	683,892	556,223	552,415	340,484
2014 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Possible future issuance under equity compensation plan (in shares)	78,465		50,283
2015 Inducement Plan [Member]
Class of Stock [Line Items]
Possible future issuance under equity compensation plan (in shares)	165,000		165,000
Underwriting Agreement [Member]
Class of Stock [Line Items]
Outstanding Underwriting Agreement warrants (in shares)	4,218,750		0