Retirement Benefits - Components of Net Periodic Benefit Cost for Defined Benefit Plans and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 155	$ 140
Interest cost	156	212
Net amortization	136	159
Net periodic benefit cost	175	193
U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	34	208
Interest cost	461	764
Expected return on plan assets	(899)	(801)
Net amortization and settlement effect	744	487
Net periodic benefit cost	340	658
Non-U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	540	464
Interest cost	263	365
Expected return on plan assets	(291)	(264)
Net amortization and settlement effect	426	284
Net periodic benefit cost	$ 938	$ 849