Other (Income) Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
gain loss on sale of asset [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	$ (346)	$ (618)	$ (408)
Investment Income [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	(332)	(506)	(383)
Interest Income [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	0	0	(56)
Foreign Currency Gain (Loss) [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	916	1,832	4,507
Rents and Royalties Income (Loss) [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	(454)	(420)	(484)
gain loss on insurance recovery [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	(477)	(632)	493
Other Income [Member]
Other operating expenses [Line Items]
Other Nonoperating Income (Expense)	$ (693)	$ (344)	$ 3,669