Fair Value Measurements (Summary of Assets and Liabilities at Fair Value) (Schedule) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Assets:
Derivative instruments:	$ 1,600.5	$ 1,827.5
SMAs	2,986.5
Other investments	934.2
Total investments	3,920.7	1,289.2
Total assets	5,521.2	3,116.7
Liabilities:
Derivative instruments:	873.3	1,582.7
Debt		45.6
Total liabilities	873.3	1,628.3
Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
SMAs	878.0
Other investments	415.5
Total investments	1,293.5	869.2
Total assets	1,293.5	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:	559.5	1,164.1
SMAs	2,108.5
Other investments	0.0
Total investments	2,108.5	0.0
Total assets	2,668.0	1,164.1
Liabilities:
Derivative instruments:		1,562.8
Debt		45.6
Total liabilities	873.3	1,608.4
Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	1,041.0	663.4
SMAs	0.0
Other investments	518.7
Total investments	518.7	420.0
Total assets	1,559.7	1,083.4
Liabilities:
Derivative instruments:		19.9
Debt		0.0
Total liabilities	0.0	19.9
Cross-currency and interest rate derivative contracts
Assets:
Derivative instruments:	556.7	1,157.2
Liabilities:
Derivative instruments:	870.7	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:	556.7	1,157.2
Liabilities:
Derivative instruments:	870.7	1,561.6
Cross-currency and interest rate derivative contracts | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0	19.9
Equity-related derivative instruments
Assets:
Derivative instruments:	1,041.0	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:	1,041.0	663.4
Foreign currency forward and option contracts
Assets:
Derivative instruments:	2.3	6.0
Liabilities:
Derivative instruments:	2.5	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:	2.3	6.0
Liabilities:
Derivative instruments:	2.5	1.2
Foreign currency forward and option contracts | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0	0.0
Other
Assets:
Derivative instruments:	0.5	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:	0.5	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