Retirement Benefits - Amounts in Accumulated Other Comprehensive Income Loss Expected to be Recognized as Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	$ 202	$ 46
Net loss (gain)	13,414	21,432
Total	13,616	21,478
Pension Benefits | Non-U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	(92)	(100)
Net loss (gain)	24,536	19,304
Total	24,444	19,204
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost (credit)	(2,914)	(46)
Net loss (gain)	(2,266)	(6,009)
Total	$ (5,180)	$ (6,055)