Commitments and Contingencies - Minimum lease commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Minimum lease commitments, Payments due by period:
2021	$ 918
2022	4,679
2023	3,160
2024	2,914
2025	2,508
Thereafter	38,367
Total future minimum lease payments	52,546
Less: Imputed interest	(18,059)
Total operating lease liabilities	34,487
Operating lease liability, current	$ 4,162	$ 4,148
Operating Lease, Liability, Current, Statement of Financial Position	Accrued expenses and other current liabilities
Long-term operating lease liabilities	$ 30,325	$ 6,305
Total operating lease liabilities	$ 34,487
Operating Lease, Liability, Statement of Financial Position	Long-term operating lease liabilities, Accrued expenses and other current liabilities