Operating Leases - Operating lease income and expense and other supplemental information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Lease Income and Expense
Operating lease cost	$ 1,947	$ 1,272	$ 4,500	$ 3,783
Variable lease cost	264	112	493	336
Short-term lease cost	27	52	80	92
Total lease cost	2,238	1,436	5,073	4,211
Sublease income and rental income from owned properties under operating leases	$ 263	$ 261	$ 792	$ 886