Income Taxes - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation
Tax at statutory federal rate (percent)	(21.00%)	(21.00%)
State tax, net of federal benefit (percent)	(4.10%)	(5.30%)
Tax credits (percent)	(0.70%)	(0.70%)
Change in deferred tax valuation allowance (percent)	25.80%	26.20%
Other (percent)	(0.00%)	0.80%
Total income tax expense (percent)	(0.00%)	(0.00%)

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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