Leases - Components of lease expense and other information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lease cost
Amortization of right-of-use assets	$ 391	$ 290
Interest on lease liabilities	82	50
Operating lease cost	1,831	910
Variable lease cost	175	72
Short-term lease cost	5	14
Sublease income	(75)
Total lease cost	$ 2,409	$ 1,336
Weighted-average remaining lease term (years), Operating leases	4 years 9 months 26 days	3 years 11 months 12 days
Weighted-average remaining lease term (years), Finance leases	2 years 9 months 18 days	2 years 7 months 24 days
Weighted-average discount rate, Operating leases	5.30%	5.00%
Weighted-average discount rate, Finance leases	5.80%	5.50%