Retirement Benefits - Amounts in Accumulated Other Comprehensive Income Loss Expected to be Recognized As Components of Net Periodic Benefit Cost During 2012 (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	$ (339)
Net loss	3,627
Total	3,288
Pension Benefit Plan | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	24
Net loss	2,716
Total	2,740
Pension Benefit Plan | Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	3
Net loss	1,282
Total	1,285
Other Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	(366)
Net loss	(371)
Total	$ (737)