Retirement Benefits Fair Value Pension Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 757.6	$ 835.7
Employer stock included in plan assets	34.7	37.6
Investments Priced Using Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92.4	78.1
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62.0	152.8
US Large-Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29.0	35.1
US Mid-Cap and Small-Cap Growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.2	41.5
International Large-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.7	23.4
Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.8	11.3
US Treasuries
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	186.4	57.7
Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	99.6	214.1
Asset Backed Securities and Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	126.6	87.9
Equity/Debt Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.5	8.1
Derivative Liability
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(0.7)	(0.5)
Alternative Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	158.3	188.2
Alternative Investment Funds | Investments Priced Using Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92.4	78.1
Common Pooled Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.2	16.1
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	237.6	381.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62.0	152.8
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Large-Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29.0	35.1
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Mid-Cap and Small-Cap Growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.2	41.5
Quoted Prices in Active Markets for Identical Assets (Level 1) | International Large-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.7	23.4
Quoted Prices in Active Markets for Identical Assets (Level 1) | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.8	11.3
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasuries
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.3	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset Backed Securities and Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.4
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity/Debt Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.6	7.1
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivative Liability
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(0.7)	(0.5)
Quoted Prices in Active Markets for Identical Assets (Level 1) | Alternative Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65.9	110.1
Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Pooled Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.8	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	427.2	376.4
Quoted Prices in Active Markets for Similar Assets (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | US Large-Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | US Mid-Cap and Small-Cap Growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | International Large-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | US Treasuries
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	186.4	57.7
Quoted Prices in Active Markets for Similar Assets (Level 2) | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98.9	214.1
Quoted Prices in Active Markets for Similar Assets (Level 2) | Asset Backed Securities and Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	126.6	87.5
Quoted Prices in Active Markets for Similar Assets (Level 2) | Equity/Debt Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	1.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | Derivative Liability
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | Alternative Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | Common Pooled Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.4	16.1
Unobservable inputs for which little or no market data exists (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | US Large-Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | US Mid-Cap and Small-Cap Growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | International Large-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | US Treasuries
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Asset Backed Securities and Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Equity/Debt Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Derivative Liability
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Alternative Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Unobservable inputs for which little or no market data exists (Level 3) | Common Pooled Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ 0.0