Income Taxes - Net operating loss carryforwards and Tax credit carryforwards (Details)	Dec. 31, 2019 USD ($)
Income Taxes
Net operating loss carryforwards	$ 53,600,000
Federal
Income Taxes
Net operating loss carryforwards	19,500,000
Research credit carryforwards | Federal
Income Taxes
Tax credit carryforwards	1,700,000
Research credit carryforwards | State
Income Taxes
Tax credit carryforwards	437,000
After tax year 2017 | Federal
Income Taxes
Net operating loss carryforwards	$ 31,800,000