Retirement Benefits (Details 10) - Pension Benefits [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 2,737.4	$ 2,727.7
Accumulated benefit obligation	2,718.0	2,710.7
Fair value of plan assets	$ 2,035.1	$ 1,894.6

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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