Derivative Financial Instruments and Hedging Activities - Schedule of Fair Value by Balance Sheet Location (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	$ 207.0	$ 326.1
Cash collateral	16.4	18.2
Derivative Asset, Fair Value, Gross, Total net of cash collateral	190.6	307.9
Derivative Liabilities, Fair Value, Gross	184.7	310.5
Cash collateral	0.0	38.6
Derivative Liabilities, Fair Value, Gross, Total net of cash collateral	184.7	271.9
Derivative Asset	115.2	155.8
Derivative Assets, Total net of cash collateral	98.8	137.6
Derivative Liabilities, Fair Value, Net	92.9	140.3
Derivative Liabilities, Total net of cash collateral	$ 92.9	$ 101.7

Derivative Asset, Fair Value, Gross, Amount Offset Against Collateral

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Derivative Liability, Fair Value, Gross, Amount Offset Against Collateral

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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