Financial Instruments (Narrative) (Details) € in Millions, ¥ in Millions, £ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 EUR (€)	Sep. 30, 2020 JPY (¥)	Sep. 30, 2020 GBP (£)	Aug. 31, 2020 USD ($)	May 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maximum remaining maturity of foreign currency derivatives			30 days
Derivatives used in net investment hedge, net of tax	$ 4,290.0		$ 4,290.0							$ 4,100.0
Percentage of long-term fixed-rate notes to floating rates through the use of interest rate swaps converted	9.00%		9.00%		9.00%	9.00%	9.00%
Pretax net losses on cash flow hedges expected to be reclassified during the next 12 months	$ 16.7		$ 16.7
Alternative investments, unfunded commitments	615.0		$ 615.0
Alternative investments, unfunded commitments, payment period			10 years
Equity securities, net unrealized gains	142.5	$ 26.4	$ 884.7	$ 182.4
Available-for-sale, percentage of nonperforming assets			94.00%
Amount of receivable derecognized	708.1		$ 708.1							678.8
Buy U.S. Dollars Sell Euros
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, notional amount	367.5		367.5
Derivative asset, notional amount | €					€ 312.3
Buy Euros Sell U.S. Dollars
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, notional amount | €					€ 2,560.0
Derivative asset, notional amount	3,010.0		3,010.0
Buy U.S. Dollars Sell Japanese Yen
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, notional amount	302.3		302.3
Derivative asset, notional amount | ¥						¥ 31,810
Buy British Pounds and Sell U.S. Dollars
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, notional amount | £							£ 226.2
Derivative asset, notional amount	290.7		290.7
Swap U.S. Dollars to Euro
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, notional amount	3,160.0		3,160.0
Swap Swiss Francs to U.S. Dollars
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, notional amount	1,000.0		1,000.0
Foreign Currency Denominated Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, including current portion	5,740.0		5,740.0							$ 5,490.0
Senior Notes Due April 2050 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount								$ 250.0	$ 1,000.0
Stated interest rate								2.25%	2.25%
Senior Notes Due August 2060 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount								$ 850.0
Stated interest rate								2.50%
Designated as Hedging Instrument | Cash Flow Hedging | Forward-starting interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, notional amount	$ 1,750.0		$ 1,750.0