v3.10.0.1
Fair Value Measurements (Summary of Assets and Liabilities at Fair Value) (Schedule) (Details) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Assets:    
Derivative instruments: $ 2,221.3 $ 2,127.7
Investments 2,164.1 2,315.3
Total assets 4,385.4 4,443.0
Liabilities:    
Derivative instruments: 1,646.9 1,781.2
Debt 881.7 926.6
Total liabilities 2,528.6 2,707.8
Quoted prices in active markets for identical assets (Level 1)    
Assets:    
Derivative instruments: 0.0 0.0
Investments 1,717.1 1,908.7
Total assets 1,717.1 1,908.7
Liabilities:    
Derivative instruments: 0.0 0.0
Debt 600.6 621.7
Total liabilities 600.6 621.7
Significant other observable inputs (Level 2)    
Assets:    
Derivative instruments: 1,728.7 1,566.6
Investments 0.0 0.0
Total assets 1,728.7 1,566.6
Liabilities:    
Derivative instruments: 1,637.2 1,772.4
Debt 281.1 304.9
Total liabilities 1,918.3 2,077.3
Significant unobservable inputs (Level 3)    
Assets:    
Derivative instruments: 492.6 561.1
Investments 447.0 406.6
Total assets 939.6 967.7
Liabilities:    
Derivative instruments: 9.7 8.8
Debt 0.0 0.0
Total liabilities 9.7 8.8
Cross-currency and interest rate derivative contracts    
Assets:    
Derivative instruments: 1,715.7 1,548.9
Liabilities:    
Derivative instruments: 1,640.6 1,767.9
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: 1,715.0 1,548.7
Liabilities:    
Derivative instruments: 1,632.6 1,764.5
Cross-currency and interest rate derivative contracts | Significant unobservable inputs (Level 3)    
Assets:    
Derivative instruments: 0.7 0.2
Liabilities:    
Derivative instruments: 8.0 3.4
Equity-related derivative instruments:    
Assets:    
Derivative instruments: 491.9 560.9
Liabilities:    
Derivative instruments: 1.7 5.4
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: 491.9 560.9
Liabilities:    
Derivative instruments: 1.7 5.4
Foreign currency forward and option contracts    
Assets:    
Derivative instruments: 13.6 17.1
Liabilities:    
Derivative instruments: 4.5 7.9
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: 13.6 17.1
Liabilities:    
Derivative instruments: 4.5 7.9
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: 0.1 0.8
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: 0.1 0.8
Liabilities:    
Derivative instruments: 0.1  
Other | Significant unobservable inputs (Level 3)    
Assets:    
Derivative instruments: 0.0 $ 0.0
Liabilities:    
Derivative instruments: $ 0.0