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 Income (Expense), Nonoperating, Net	$ 356	$ 147	$ 298	$ 192
Other Nonoperating Income	1	1	3	0
Other Nonoperating Expense	0	0	0	(1)
Insurance policy expense	(12)	(12)	(24)	(24)
Defined Benefit Plan, Non-service Costs	(1,127)	(749)	(1,763)	(1,498)
Other expense, net	$ (782)	$ (613)	$ (1,486)	$ (1,331)