Derivative Instruments Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative assets, fair value	$ 93.4	$ 35.6
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, fair value	90.7	35.6
Designated as Hedging Instrument [Member] | Treasury Lock Agreements [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, fair value	90.7	35.6
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, fair value	2.7	0.0
Not Designated as Hedging Instrument [Member] | Foreign Currency Forward Contracts [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, fair value	$ 2.7	$ 0.0