Other Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Income and Expenses [Abstract]
Other Nonoperating Income	$ 482	$ 3,431
Interest (expense) income	(136)	375
Insurance Policy Expense (Income), Net	(77)	(79)
Defined Benefit Plan, Non-service Costs	(29)	(513)
Other Nonoperating Expense	(9)	(10)
Other income, net	$ 231	$ 3,204