Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Commitments
Rental expense	$ 200	$ 200	$ 400	$ 300
Future minimum payments for operating leases
Remainder of 2017	303		303
2018	456		456
2019	449		449
2020	358		358
2021 and thereafter	997		997
Total	2,563		2,563
Future minimum payments for other commitments
Remainder of 2017	8,125		8,125
2018	7,732		7,732
2019	2,385		2,385
2020	622		622
2021 and thereafter	10		10
Total	18,874		18,874
Future minimum payments for operating leases and other commitments
Remainder of 2017	8,428		8,428
2018	8,188		8,188
2019	2,834		2,834
2020	980		980
2021 and thereafter	1,007		1,007
Total	$ 21,437		$ 21,437