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Financial Instruments and Fair Value Measurements (Summary of Carrying Values and Fair Values of Fixed Rate Debt) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity security with readily determinable fair value			$ 101.9
Investment in equity security		$ 50.0	50.0	$ 0.0	$ 50.0
Equity security without a readily determinable fair value			50.0
Net gains recognized during the period on equity securities			131.5	25.7	0.0
Less: Net gains recognized during the period on equity securities sold during the period			(63.4)	0.0
Unrealized gains recognized during the reporting period on equity securities still held at the reporting date			68.1	25.7
Proceeds from the sale of equity securities			105.4	0.0	$ 0.0
Subsequent Event [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Proceeds from the sale of equity securities	$ 109.4
Fixed Rate Debt [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed rate debt			2,101.8	1,934.1
Fixed Rate Debt [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed rate debt			$ 2,341.1	$ 2,001.8

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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