Financing Components of Debt (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Jun. 20, 2016	Jun. 16, 2016
Debt Instrument [Line Items]
Long-term borrowings, carrying value	$ 4,056,200,000	$ 3,358,000,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	948,600,000
US Dollar-Denominated Commercial Paper [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	665,100,000	347,900,000
Euro Denominated Commercial Paper [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	282,700,000	26,800,000
Senior Unsecured Notes due 2019 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	298,900,000	298,300,000
Interest rate			1.80%
Senior Unsecured Notes due 2021 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	745,900,000	744,800,000
Interest rate			2.35%
Senior Unsecured Notes due 2026 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	891,000,000	890,100,000
Interest rate			3.15%
Senior Unsecured Notes due 2046 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	546,800,000	546,800,000
Interest rate			4.30%
Other Debt [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	3,400,000	3,300,000
Term Loan [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	$ 500,000,000	500,000,000		$ 500,000,000
Interest rate	2.69%
Yen Term Loan [Member]
Debt Instrument [Line Items]
Long-term borrowings, carrying value	$ 122,400,000	$ 0