Other Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Income and Expenses [Abstract]
Interest (expense) income	$ (15)	$ 61	$ 141	$ 204
Other nonoperating income	42	75	48	230
Other nonoperating expense	(3)	(4)	(7)	(7)
Insurance policy expense	(47)	(49)	(94)	(98)
Defined Benefit Plan, Non-service Costs	(486)	(678)	(957)	(1,356)
Other expense, net	$ (509)	$ (595)	$ (869)	$ (1,027)