Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands |
Jun. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | $ 450 | $ 228 |
| Less: accumulated depreciation | (53) | (14) |
| Total property and equipment, net | 397 | 214 |
| Computer Equipment [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 140 | 56 |
| Software [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 11 | 9 |
| Lab Equipment [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 224 | $ 163 |
| Leasehold Improvements [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | $ 75 |