Schedule of Net Periodic Pension Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Service cost	$ 924	$ 941	$ 1,852	$ 1,927
Interest cost	535	650	1,060	1,283
Expected return on plan assets	(147)	(133)	(293)	(259)
Settlements and other	0	(4)	0	(7)
Amortization of actuarial net loss	403	334	794	661
Amortization of unrecognized prior service costs	15	16	30	31
Net periodic benefit cost	$ 1,730	$ 1,804	$ 3,443	$ 3,636