Derivative Financial Instruments and Hedging Activities Schedule of Fair Value by Balance Sheet Location (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	$ 198.7	$ 114.9
Cash collateral	19.0	6.1
Derivative Asset, Fair Value, Gross, Total net of cash collateral	179.7	108.8
Derivative Liabilities, Fair Value, Gross	180.0	103.8
Cash collateral	24.2	25.6
Derivative Liabilities, Fair Value, Gross, Total net of cash collateral	155.8	78.2
Derivative Assets, Fair Value, Net	97.8	72.1
Derivative Assets, Total net of cash collateral	78.8	66.0
Derivative Liabilities, Fair Value, Net	79.1	60.9
Derivative Liabilities, Total net of cash collateral	$ 54.9	$ 35.3