Income Taxes - Effective Tax Rate (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S. federal provision at statutory rate	21.00%	21.00%
State income taxes, net of federal benefit	0.70%	2.90%
Tax credits	0.60%	1.90%
Fair value of financial instruments	(15.60%)	(6.80%)
Stock-based compensation expense	(0.40%)	(0.60%)
Uncertain tax benefits	(0.30%)	(0.90%)
Change in valuation allowance	(6.00%)	(17.50%)
Effective tax rate	0.00%	(0.00%)

Effective Income Tax Rate Reconciliation, Fair Value Of Financial Instruments, Percent

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 12
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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.

+ References

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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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 income tax contingencies. Includes, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

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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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