Leases - Operating lease costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 707	$ 1,395
Finance lease cost:
Amortization of right-of-use assets	77	77
Interest on lease liabilities	112	112
Operating cash flows from operating leases	524	1,024
Operating cash flows from finance leases	111	111
Financing cash flows from finance leases	$ 0	$ 0