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, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 1,016	$ 1,279	$ 1,162
Interest cost		3,043	3,770	4,037
Expected return on plan assets		(4,777)	(4,910)	(5,430)
Settlement loss recognized	$ (3,500)	3,339	0	0
Net amortization		3,226	3,422	2,187
Net periodic benefit cost		5,847	3,561	1,956
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		1,627	1,506	1,331
Interest cost		1,429	1,734	2,345
Expected return on plan assets		(993)	(1,114)	(1,297)
Settlement loss recognized		215	0	0
Net amortization		1,008	1,931	1,400
Net periodic benefit cost		3,286	4,057	3,779
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		601	673	714
Interest cost		811	833	932
Net amortization		(705)	(414)	(474)
Net periodic benefit cost		$ 707	$ 1,092	$ 1,172