Leases - Components of lease expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Finance lease cost:
Amortization of assets	$ 1,038	$ 386
Interest on lease liabilities	489	245
Operating lease expense:
Operating lease cost	2,263	3,333
Variable lease cost	264	210
Sublease income	(48)	(46)
Total lease costs	$ 4,006	$ 4,128