Income Taxes - Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective income tax rate reconciliation
Tax benefit at U.S. federal statutory rate	$ (50,788)	$ (42,471)	$ (17,629)
Stock based compensation		(68)	(47)
Other nondeductible expenses	5	1	14
State income taxes benefit before valuation allowance, net of federal benefit	(19,622)	(16,580)	(6,613)
Increase in domestic valuation allowance	79,258	66,593	26,843
Research and development credit	(9,002)	(7,472)	(2,636)
Other adjustments	149	(3)	68
Income tax expense (benefit)		$ 0	$ 0

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

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount 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 exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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