Stockholders' Equity - Reserved Shares of Authorized but Unissued Common Stock (Detail) - shares	Jun. 30, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Total reserved shares of common stock	5,124,169	3,951,819
Common Stock Warrants [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	1,667,398	1,667,398
Equity Incentive Plans [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	3,456,771	2,284,421