Fair Value Measurements (Summary of Assets and Liabilities at Fair Value) (Schedule) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets:
Derivative instruments:	$ 2,547.8	$ 2,496.7
Investments	1,187.1	1,174.8
Total assets	3,734.9	3,671.5
Liabilities:
Derivative instruments:	1,344.4	1,370.7
Debt	262.2	248.6
Total liabilities	1,606.6	1,619.3
Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
Investments	762.5	755.9
Total assets	762.5	755.9
Liabilities:
Derivative instruments:	0.0	0.0
Debt	0.0	0.0
Total liabilities	0.0	0.0
Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	1,786.4	1,750.1
Investments	0.0	0.0
Total assets	1,786.4	1,750.1
Liabilities:
Derivative instruments:	1,328.2	1,354.9
Debt	262.2	248.6
Total liabilities	1,590.4	1,603.5
Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	761.4	746.6
Investments	424.6	418.9
Total assets	1,186.0	1,165.5
Liabilities:
Derivative instruments:	16.2	15.8
Debt	0.0	0.0
Total liabilities	16.2	15.8
Cross-currency and interest rate derivative contracts
Assets:
Derivative instruments:	1,778.0	1,742.8
Liabilities:
Derivative instruments:	1,336.2	1,368.7
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:	1,777.4	1,742.5
Liabilities:
Derivative instruments:	1,321.5	1,354.3
Cross-currency and interest rate derivative contracts | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	0.6	0.3
Liabilities:
Derivative instruments:	14.7	14.4
Equity-related derivative instruments
Assets:
Derivative instruments:	760.8	746.3
Liabilities:
Derivative instruments:	1.3	1.4
Equity-related derivative instruments | Quoted prices in active markets for identical assets (Level 1)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0	0.0
Equity-related derivative instruments | Significant other observable inputs (Level 2)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.0	0.0
Equity-related derivative instruments | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	760.8	746.3
Liabilities:
Derivative instruments:	1.3	1.4
Foreign currency forward and option contracts
Assets:
Derivative instruments:	8.4	7.2
Liabilities:
Derivative instruments:	6.9	0.5
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:	8.4	7.2
Liabilities:
Derivative instruments:	6.7	0.5
Foreign currency forward and option contracts | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	0.0	0.0
Liabilities:
Derivative instruments:	0.2	0.0
Other
Assets:
Derivative instruments:	0.6	0.4
Liabilities:
Derivative instruments:	0.0	0.1
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:	0.6	0.4
Liabilities:
Derivative instruments:		0.1
Other | Significant unobservable inputs (Level 3)
Assets:
Derivative instruments:	$ 0.0	0.0
Liabilities:
Derivative instruments:		$ 0.0