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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

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- Definition 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. + 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)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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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 + Details
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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 + Details
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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 + Details
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