Retirement Benefits (Details 12) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 1,894.6	$ 1,962.3
Net Realized and Unrealized Gains (Losses)	304.1	79.7
Fair value of plan assets at end of year	2,129.6	1,894.6
Fixed income and cash equivalents [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	412.2
Fair value of plan assets at end of year	501.1	412.2
Floating rate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	225.5
Fair value of plan assets at end of year	169.9	225.5
Private equity [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	142.6
Fair value of plan assets at end of year	137.5	142.6
Hedge funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	283.9
Fair value of plan assets at end of year	307.4	283.9
Real estate and other [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	96.5
Fair value of plan assets at end of year	93.9	96.5
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.2	194.6
Net Realized and Unrealized Gains (Losses)		4.8
Net Purchases, Issuances and Settlements		(199.2)
Net Transfers Into (Out Of) Level 3		0.0
Fair value of plan assets at end of year	0.0	0.2
Significant Unobservable Inputs (Level 3) [Member] \| Fixed income and cash equivalents [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.2	0.3
Net Realized and Unrealized Gains (Losses)		0.0
Net Purchases, Issuances and Settlements		(0.1)
Net Transfers Into (Out Of) Level 3		0.0
Fair value of plan assets at end of year	0.0	0.2
Significant Unobservable Inputs (Level 3) [Member] \| Floating rate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.0	194.3
Net Realized and Unrealized Gains (Losses)		4.8
Net Purchases, Issuances and Settlements		(199.1)
Net Transfers Into (Out Of) Level 3		0.0
Fair value of plan assets at end of year	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] \| Private equity [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.0
Fair value of plan assets at end of year	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] \| Hedge funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.0
Fair value of plan assets at end of year	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] \| Real estate and other [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.0
Fair value of plan assets at end of year	$ 0.0	$ 0.0

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from purchases, sales and settlements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(02)(B)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(02)(C)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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