Income Taxes - Operating loss carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Income tax benefits	$ 0	$ 0
Net operating loss carryforwards subject to expiration	3,200
Net operating loss carryforwards limited in usage	89,900
Uncertain tax position	0
Research and development tax credit carryforwards
Operating Loss Carryforwards [Line Items]
Increase in valuation allowance	15,700	$ 8,200
Federal
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	93,100
Tax credit carryforwards	2,300
State
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	88,000
Tax credit carryforwards	$ 1,200