Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating lease costs
Single lease costs	$ 1,038	$ 1,043	$ 3,114	$ 3,089
Variable lease costs	469	428	1,436	1,311
Sublease income:
Sublease income	(475)	(475)	(1,425)	(1,425)
Total operating lease costs	$ 1,032	$ 996	$ 3,125	$ 2,975