Retirement Benefits - Components of Net Periodic Benefit Cost for Defined Benefit Plans and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 154	$ 140	$ 309	$ 280
Interest cost	157	212	313	424
Net amortization	(136)	(158)	(272)	(317)
Net periodic benefit cost	175	194	350	387
U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	35	209	69	417
Interest cost	190	764	651	1,528
Expected return on plan assets	(978)	(801)	(1,877)	(1,602)
Net amortization and settlement effect			585	973
Net amortization	(159)	486
Net periodic benefit cost	(912)	658	(572)	1,316
Non-U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	541	460	1,081	924
Interest cost	263	361	526	726
Expected return on plan assets	(291)	(262)	(582)	(526)
Net amortization and settlement effect			852	564
Net amortization	426	280
Net periodic benefit cost	$ 939	$ 839	$ 1,877	$ 1,688