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Income Taxes - Reconciliation of effective tax rate (Details)
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Reconciliation of the effective tax rate to the U.S. Federal statutory rate      
Federal tax benefit at statutory rate 21.00% 21.00% 21.00%
State tax, net of Federal benefit 8.00% 9.00% 14.00%
Change in valuation allowance (22.00%) (26.00%) (24.00%)
Research and development tax credits 2.00% 3.00% 19.00%
Share based Compensation (1.00%) (1.00%) (10.00%)
162(m) covered employees compensation limitation     (6.00%)
FIN48 Reserve   (1.00%) (161.00%)
Deconsolidation gain (7.00%) (3.00%) 174.00%
Gain on transfer of intellectual property     (20.00%)
Prior year federal true-up   (1.00%) (7.00%)
Other (1.00%) (1.00%)  
Effective income tax rate 0.00% 0.00% 0.00%