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Fair Value Disclosure (Details) $ in Millions	12 Months Ended
Fair Value Disclosure (Details) $ in Millions	Dec. 31, 2020 USD ($) Instrument	Dec. 31, 2019 USD ($) Instrument	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	$ 7,170.7	$ 6,457.3
Derivative Liability	0.0	13.6
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	1.4
Asset Impairment Charges	0.3	6.6	$ 9.0
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0.0	13.6
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0.0	13.6
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0.0	0.0
Portfolio Management [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	0.0	6.2	4.5
Changes Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	0.0		3.0
Reported Value Measurement [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	1.7	1.6
Interest Rate Contract [Member] \| Fair Value, Recurring [Member] \| Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0.0	0.6
Interest Rate Contract [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0.0	0.6
Interest Rate Contract [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 0.0	$ 0.0
Interest Rate Contract [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Number of Instruments Held \| Instrument	(5)	(8)
Interest Rate Contract [Member] \| Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Number of Instruments Held \| Instrument	(1)	(7)
Interest Rate Contract [Member] \| Other Nonoperating Income (Expense) [Member] \| Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effective portion reclassified from accumulated other comprehensive loss		$ 0.0	$ 0.0