Lease Agreements - Future minimum rental payments under operating and capital leases (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital leases minimum payments for 2016	$ 96
Capital leases minimum payments for 2017	0
Capital leases minimum payments for 2018	0
Capital leases minimum payments for 2019	0
Capital leases minimum payments for 2020	0
Capital leases minimum payments for later years	0
Capital leases minimum payments total	96
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases minimum payments for 2016	8,291
Operating leases minimum payments for 2017	8,073
Operating leases minimum payments for 2018	6,295
Operating leases minimum payments for 2019	5,545
Operating leases minimum payments for 2020	5,224
Operating leases minimum payments for later years	16,545
Operating leases minimum payments total	49,973
Built-to-suit Lease, Future Minimum Payments Due	17,254
Built-to-suit Lease, Future Minimum Payments Due, Next Twelve Months	0
Built-to-suit Lease, Future Minimum Payments Due in Two Years	1,180
Built-to-suit Lease, Future Minimum Payments Due in Three Years	1,203
Built-to-suit Lease, Future Minimum Payments Due in Four Years	1,227
Built-to-suit Lease, Future Minimum Payments Due in Five Years	1,252
Built-to-suit Lease, Future Minimum Payments Due Thereafter	$ 12,392