Derivative Instruments, Hedging Activities and Fair Value Measurements, Liability Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Interest rate derivatives [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 258.3	$ 13.5
Gross Amounts Offset in the Balance Sheet	0.0	0.0
Amounts of Liabilities Presented in the Balance Sheet	258.3	13.5
Financial Instruments	0.0	0.0
Cash Collateral Received	0.0	0.0
Cash Collateral Paid	0.0	0.0
Amounts That Would Have Been Presented On Net Basis	258.3	13.5
Commodity Derivatives [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	272.2	116.2
Gross Amounts Offset in the Balance Sheet	0.0	0.0
Amounts of Liabilities Presented in the Balance Sheet	272.2	116.2
Financial Instruments	(267.0)	(115.3)
Cash Collateral Received	0.0	0.0
Cash Collateral Paid	0.0	0.0
Amounts That Would Have Been Presented On Net Basis	$ 5.2	$ 0.9