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Retirement Benefits (Details 11) - Pension Benefits [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,046.4	$ 1,902.1	$ 1,772.2
NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,549.0	1,455.9
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	296.0	274.1
Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	201.4	172.1
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities: Other U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	452.0	443.6
Equity Securities: Other U.S. equities [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	264.7	254.7
Equity Securities: Other U.S. equities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	187.3	188.9
Equity Securities: Other U.S. equities [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities: Other U.S. equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities: International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	477.1	326.1
Equity Securities: International equities [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	448.7	299.6
Equity Securities: International equities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.4	26.5
Equity Securities: International equities [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities: International equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed income and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	588.0	650.7
Fixed income and cash equivalents [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	306.3	419.9
Fixed income and cash equivalents [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	80.3	58.7
Fixed income and cash equivalents [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	201.4	172.1
Fixed income and cash equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Floating rate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.4	51.0
Floating rate [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.4	51.0
Floating rate [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Floating rate [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Floating rate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Private equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	130.0	129.0
Private equity [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	130.0	129.0
Private equity [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Private equity [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Private equity [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	325.0	263.9
Hedge funds [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	325.0	263.9
Hedge funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Hedge funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Hedge funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Real estate and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.9	37.8
Real estate and other [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.9	37.8
Real estate and other [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Real estate and other [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Real estate and other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ 0.0

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