Fair Value Measurements (Assets and Liabilities at Fair Value) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	$ 606.2	$ 843.9
SMAs	77.9	433.1
Other investments	2,976.6	2,810.2
Total investments	3,054.5	3,243.3
Total assets	3,660.7	4,087.2
Derivative instruments:	97.5	186.4
Total liabilities	97.5	186.4
Quoted prices in active markets for identical assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
SMAs	0.0	127.0
Other investments	1,699.9	1,546.3
Total investments	1,699.9	1,673.3
Total assets	1,699.9	1,673.3
Total liabilities	0.0	0.0
Significant other observable inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	432.4	630.5
SMAs	77.9	306.1
Other investments	0.1	0.1
Total investments	78.0	306.2
Total assets	510.4	936.7
Total liabilities	97.5	186.4
Significant unobservable inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	173.8	213.4
SMAs	0.0	0.0
Other investments	1,276.6	1,263.8
Total investments	1,276.6	1,263.8
Total assets	1,450.4	1,477.2
Total liabilities	0.0	0.0
Cross-currency and interest rate derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	427.0	623.2
Derivative instruments:	91.1	183.1
Cross-currency and interest rate derivative contracts | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
Derivative instruments:	0.0	0.0
Cross-currency and interest rate derivative contracts | Significant other observable inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	427.0	623.2
Derivative instruments:	91.1	183.1
Cross-currency and interest rate derivative contracts | Significant unobservable inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
Derivative instruments:	0.0	0.0
Equity-related derivative instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	173.8	213.4
Equity-related derivative instruments | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
Equity-related derivative instruments | Significant other observable inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
Equity-related derivative instruments | Significant unobservable inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	173.8	213.4
Foreign currency forward and option contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	5.4	6.5
Derivative instruments:	6.2	3.3
Foreign currency forward and option contracts | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
Derivative instruments:	0.0	0.0
Foreign currency forward and option contracts | Significant other observable inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	5.4	6.5
Derivative instruments:	6.2	3.3
Foreign currency forward and option contracts | Significant unobservable inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.0
Derivative instruments:	0.0	0.0
Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments	0.0	0.8
Derivative instruments:	0.2	0.0
Other | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments		0.0
Derivative instruments:	0.0
Other | Significant other observable inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments		0.8
Derivative instruments:	0.2
Other | Significant unobservable inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments		$ 0.0
Derivative instruments:	$ 0.0