Derivative Instruments, Hedging Activities and Fair Value Measurements, Liability Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Interest rate derivatives [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 193.6	$ 13.5
Gross Amounts Offset in the Balance Sheet	0.0	0.0
Amounts of Liabilities Presented in the Balance Sheet	193.6	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	193.6	13.5
Commodity Derivatives [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	190.2	116.2
Gross Amounts Offset in the Balance Sheet	0.0	0.0
Amounts of Liabilities Presented in the Balance Sheet	190.2	116.2
Financial Instruments	(139.4)	(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	$ 50.8	$ 0.9