Retirement Benefits - Information Comparing Plan Assets to Plan Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Total
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	$ 824.8	$ 769.8
Accumulated benefit obligation	1,010.5	953.2
Projected benefit obligation	1,030.1	973.8
U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	777.2	728.5
Accumulated benefit obligation	890.3	845.9
Projected benefit obligation	890.3	845.9
Non-U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	47.6	41.3
Accumulated benefit obligation	120.2	107.3
Projected benefit obligation	$ 139.8	$ 127.9

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- Definition

Amount of accumulated benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

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- Definition

Fair value of plan assets for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921

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