Leases - Components of lease expense and other information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Lease cost
Amortization of right-of-use assets	$ 391	$ 411	$ 782	$ 701
Interest on lease liabilities	77	59	159	109
Operating lease cost	1,279	961	3,110	1,871
Variable lease cost	78	115	253	187
Short-term lease cost	14	5	19	19
Sublease income	(226)		(452)
Total lease cost	$ 1,613	$ 1,551	$ 3,871	$ 2,887
Weighted-average remaining lease term (years), Operating leases	4 years 7 months 24 days	5 years 1 month 24 days	4 years 7 months 24 days	5 years 1 month 24 days
Weighted-average remaining lease term (years), Finance leases	2 years 7 months 2 days	2 years 8 months 23 days	2 years 7 months 2 days	2 years 8 months 23 days
Weighted-average discount rate, Operating leases	5.30%		5.30%		5.30%
Weighted-average discount rate, Finance leases	5.80%		5.80%		5.70%