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Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Percent of pre-tax income:      
U.S. federal statutory income tax rate 21.00% 21.00% 21.00%
State taxes, net of federal benefit 14.80% 10.90% 18.50%
Permanent items 0.20% (1.00%) 4.00%
Impact of state rate changes 0.10% 0.10% (0.20%)
Research and development credit 3.10% 2.80% (2.40%)
Change in valuation allowance (34.80%) (33.60%) (42.60%)
Effective income tax rate 4.40% 0.20% (1.70%)