Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands |
Dec. 31, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Deferred tax assets: | ||
| Net operating loss carryforwards | $ 93,165 | $ 72,984 |
| Deferred rent | 235 | 127 |
| Accrued bonus | 0 | 68 |
| Accrued compensation | 326 | 539 |
| Stock-based compensation | 6,224 | 3,266 |
| Other reserves and accruals | 4 | 2 |
| Property and equipment | 322 | 16 |
| Deferred revenue | 3,017 | 2,173 |
| Deferred Tax Assets, Gross | 103,293 | 79,175 |
| Valuation allowance | (103,293) | (79,175) |
| Net deferred tax assets | $ 0 | $ 0 |