Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Commitments
Rental expense	$ 600	$ 200	$ 1,100	$ 400
Future minimum payments for operating leases
Remainder of 2018	1,087		1,087
2019	449		449
2020	358		358
2021	343		343
2022 and thereafter	655		655
Total	2,892		2,892
Future minimum payments for other commitments
Remainder of 2018	7,728		7,728
2019	7,964		7,964
2020	4,472		4,472
2021	3,002		3,002
2022 and thereafter	269		269
Total	23,435		23,435
Future minimum payments for operating leases and other commitments
Remainder of 2018	8,815		8,815
2019	8,413		8,413
2020	4,830		4,830
2021	3,345		3,345
2022 and thereafter	924		924
Total	$ 26,327		$ 26,327