Income Taxes - Effective Income Tax Rate Reconciliation (Details) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Effective income tax rate reconciliation | |||
| U.S. Federal statutory tax rate | (21.00%) | (35.00%) | (35.00%) |
| Deferred state taxes | (1.90%) | (1.40%) | (3.10%) |
| Common stock warrant liability | (1.00%) | 4.20% | (2.60%) |
| Provision to return and deferred tax asset adjustments | 5.90% | (2.90%) | |
| Change in unrecognized tax benefits | (0.70%) | ||
| Change in U.S. Federal statutory tax rate | 33.50% | ||
| Other, net | 0.40% | 2.00% | (1.60%) |
| Change in valuation allowance | 12.90% | (9.20%) | 45.20% |
| Total effective income tax rate | (10.60%) | 0.00% | (0.70%) |