Income Tax - Components of deferred tax assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Federal and state net operating losses	$ 41,418	$ 27,269
Research and development credits	77	77
Accruals and other	16,173	3,536
Share-based compensation	7,124	1,674
Reserve for contract contingencies and processing errors	818	2,334
Deferred revenue	3,132	695
Lease liability	3,730	4,458
Total deferred tax assets	72,472	40,043
Less valuation allowance	(68,847)	(36,327)
Total deferred tax assets, net of valuation allowance	3,625	3,716
Deferred tax liabilities
Property and equipment	(47)	(309)
Right-of-use asset	(2,728)	(3,281)
Total deferred tax liabilities	(2,775)	(3,590)
Net deferred tax assets	$ 850	$ 126