Retirement Benefits - Components of Net Periodic Benefit Cost for Defined Benefit Plans and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement loss recognized	$ 700
Pension Benefits | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 653	$ 886	$ 976
Interest cost		2,796	2,634	2,677
Expected return on plan assets		(3,319)	(3,943)	(3,832)
Settlement loss recognized		713	(1)	0
Special termination benefit recognized		276	0	0
Net amortization		1,614	2,712	2,566
Net periodic benefit cost		2,733	2,288	2,387
Pension Benefits | Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		1,844	2,105	1,975
Interest cost		1,440	1,389	1,283
Expected return on plan assets		(1,047)	(1,120)	(1,088)
Settlement loss recognized		0	(307)	234
Special termination benefit recognized		0	0	0
Net amortization		1,117	1,271	1,809
Net periodic benefit cost		3,354	3,338	4,213
Other Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		561	668	610
Interest cost		849	810	818
Net amortization		(635)	(737)	(795)
Net periodic benefit cost		$ 775	$ 741	$ 633