Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitments
Rental expense	$ 2,200	$ 700
Future minimum payments for operating leases
2019	1,571
2020	367
2021	350
2022	355
2023 and thereafter	302
Total	2,945
Future minimum payments for other commitments
2019	11,961
2020	6,229
2021	2,846
2022	489
Total	21,525
Future minimum payments for operating leases and other commitments
2019	13,532
2020	6,596
2021	3,196
2022	844
2023 and thereafter	302
Total	$ 24,470