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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 141	$ 167	$ 421	$ 502
Interest cost	212	202	636	608
Net amortization	(159)	(185)	(476)	(553)
Net periodic benefit cost	194	184	581	557
U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	484	156	901	665
Interest cost	764	669	2,292	1,975
Expected return on plan assets	(801)	(991)	(2,403)	(2,957)
Settlement loss recognized	486	0	486	0
Net amortization	487	664	1,460	2,034
Net periodic benefit cost	1,420	498	2,736	1,717
Non-U.S. | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	462	520	1,386	1,592
Interest cost	355	341	1,081	1,053
Expected return on plan assets	(258)	(276)	(784)	(848)
Settlement loss recognized	0	0	0	0
Net amortization	276	312	840	964
Net periodic benefit cost	$ 835	$ 897	$ 2,523	$ 2,761