Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments
Rental expense	$ 600	$ 300	$ 200
Future minimum payments for operating leases
2016	296
2017	388
2018	383
2019	335
2020 and thereafter	1,150
Total	2,552
Future minimum payments for other commitments
2016	7,093
2017	3,413
2018	2,561
2019	1,260
2020 and thereafter	631
Total	14,958
Future minimum payments for operating leases and other commitments
2016	7,389
2017	3,801
2018	2,944
2019	1,595
2020 and thereafter	1,781
Total	$ 17,510