Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Commitments
Rental expense	$ 100	$ 100	$ 300	$ 200
Future minimum payments for operating leases
2015	127		127
2016	59		59
2017	49		49
2018	48		48
2019 and thereafter	5		5
Total	288		288
Future minimum payments for other commitments
2015	6,096		6,096
2016	6,026		6,026
2017	2,625		2,625
2018	1,824		1,824
2019 and thereafter	2,001		2,001
Total	18,572		18,572
Future minimum payments for operating leases and other commitments
2015	6,223		6,223
2016	6,085		6,085
2017	2,674		2,674
2018	1,872		1,872
2019 and thereafter	2,006		2,006
Total	$ 18,860		$ 18,860