Non-pension Post-retirement Benefits (Pre-tax Amounts Recognized in Accumulated Other Comprehensive Loss) (Details) - Non-pension Post-retirement Benefit Plans - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ (912)	$ 4,416
Prior service cost (credit)	(1,262)	(1,463)
Total cost (credit)	(2,174)	2,953
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(80)	5,146
Prior service cost (credit)	(1,262)	(1,463)
Total cost (credit)	(1,342)	3,683
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(832)	(730)
Prior service cost (credit)	0	0
Total cost (credit)	$ (832)	$ (730)