Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating lease costs
Single lease costs	$ 1,043	$ 1,039	$ 3,089	$ 3,141
Variable lease costs	428	410	1,311	1,310
Sublease income:
Sublease income	(475)	(468)	(1,425)	(1,403)
Total operating lease costs	$ 996	$ 981	$ 2,975	$ 3,048