Fair Value Measurements (Summary of Assets and Liabilities at Fair Value) (Schedule) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets:
Derivative instruments:	$ 1,300.2	$ 1,827.5
SMAs	2,988.5
Other investments	941.4
Total investments	3,929.9	1,289.2
Total assets	5,230.1	3,116.7
Liabilities:
Derivative instruments:	1,179.8	1,582.7
Debt		45.6
Total liabilities	1,179.8	1,628.3
Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
SMAs	1,029.0
Other investments	421.5
Total investments	1,450.5	869.2
Total assets	1,450.5	869.2
Liabilities:
Derivative instruments:		0.0
Debt		0.0
Total liabilities	0.0	0.0
Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	495.4	1,164.1
SMAs	1,959.5
Other investments	0.0
Total investments	1,959.5	0.0
Total assets	2,454.9	1,164.1
Liabilities:
Derivative instruments:		1,562.8
Debt		45.6
Total liabilities	953.4	1,608.4
Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	804.8	663.4
SMAs	0.0
Other investments	519.9
Total investments	519.9	420.0
Total assets	1,324.7	1,083.4
Liabilities:
Derivative instruments:		19.9
Debt		0.0
Total liabilities	226.4	19.9
Cross-currency and interest rate derivative contracts
Assets:
Derivative instruments:	529.5	1,157.2
Liabilities:
Derivative instruments:	1,142.2	1,581.5
Cross-currency and interest rate derivative contracts | Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0	0.0
Cross-currency and interest rate derivative contracts | Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	464.4	1,157.2
Liabilities:
Derivative instruments:	920.4	1,561.6
Cross-currency and interest rate derivative contracts | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	65.1	0.0
Liabilities:
Derivative instruments:	221.8	19.9
Equity-related derivative instruments
Assets:
Derivative instruments:	739.7	663.4
Equity-related derivative instruments | Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
Equity-related derivative instruments | Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	0.0	0.0
Equity-related derivative instruments | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	739.7	663.4
Foreign currency forward and option contracts
Assets:
Derivative instruments:	30.7	6.0
Liabilities:
Derivative instruments:	37.5	1.2
Foreign currency forward and option contracts | Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0	0.0
Foreign currency forward and option contracts | Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	30.7	6.0
Liabilities:
Derivative instruments:	32.9	1.2
Foreign currency forward and option contracts | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	4.6	0.0
Other
Assets:
Derivative instruments:	0.3	0.9
Liabilities:
Derivative instruments:	0.1	0.0
Other | Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0
Other | Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	0.3	0.9
Liabilities:
Derivative instruments:	0.1
Other | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	0.0	$ 0.0
Liabilities:
Derivative instruments:	$ 0.0