Operating leases (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating leases Future Minimum Payments
Primary lease Minimum payments 2016	$ 1,000
Primary lease Minimum payments 2017	83
Primary lease Minimum payments total	1,083
Lease expenses incurred	$ 980,000	$ 961,000	$ 942,000