Retirement Benefits - Components of Net Periodic Benefit Cost for Defined Benefit Plans and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 154	$ 141	$ 463	$ 421
Interest cost	156	212	469	636
Net amortization	(135)	(159)	(407)	(476)
Net periodic (benefit) cost	175	194	525	581
U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	34	484	103	901
Interest cost	312	764	963	2,292
Expected return on plan assets	(927)	(801)	(2,804)	(2,403)
Settlement loss recognized	326	486	702	486
Net amortization and settlement effect			852	1,460
Net amortization	643	487
Net periodic (benefit) cost	388	1,420	(184)	2,736
Non-U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	539	462	1,620	1,386
Interest cost	263	355	789	1,081
Expected return on plan assets	(291)	(258)	(873)	(784)
Settlement loss recognized	0	0	0	0
Net amortization and settlement effect			1,279	840
Net amortization	427	276
Net periodic (benefit) cost	$ 938	$ 835	$ 2,815	$ 2,523