Leases - Operating lease costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating lease cost	$ 655		$ 2,050
Finance lease cost:
Amortization of right-of-use assets - finance leases	146		223
Interest on lease liabilities	228	$ 0	340	$ 0
Operating cash flows from operating leases	477		1,501
Operating cash flows from finance leases	206		317
Financing cash flows from finance leases	$ 0		$ 0