Annual report pursuant to Section 13 and 15(d)

Income Taxes - Reconciliation - (Details)

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Income Taxes - Reconciliation - (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Federal income tax computed at federal statutory tax rate 21.00% 21.00% 34.00%
State income tax, net of federal benefit 6.56% 6.01% 5.35%
Permanent items (0.89%) (0.61%) (1.57%)
Federal and state research and development credits 4.79% 4.79% 7.36%
Rate change     (31.79%)
Other (0.77%) 0.01% 0.66%
Change in valuation allowance (30.73%) (31.24%) (14.02%)
Effective income tax rate (0.04%) (0.04%) (0.01%)