Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Long-Term Debt (Commercial Paper) (Details) - USD ($)			12 Months Ended
Long-Term Debt (Commercial Paper) (Details) - USD ($)	Jul. 31, 2015	Feb. 28, 2014	Dec. 31, 2018	Dec. 31, 2017	Mar. 26, 2015
United States \| Commercial Paper
Line of Credit Facility [Line Items]
Maturity period of debt			27 days 15 hours 21 minutes 36 seconds
Maximum borrowing capacity under credit facility					$ 1,800,000,000
Weighted average interest rate on debt			2.98%
United States \| Maximum \| Commercial Paper
Line of Credit Facility [Line Items]
Maturity period of debt		397 days
Europe \| Commercial Paper
Line of Credit Facility [Line Items]
Maturity period of debt	183 days		28 days 14 hours 38 minutes 24 seconds
Weighted average interest rate on debt			(0.21%)
Carrying Value \| United States
Line of Credit Facility [Line Items]
Commercial paper			$ 632,668,000	$ 228,500,000
Carrying Value \| Europe
Line of Credit Facility [Line Items]
Commercial paper			$ 707,175,000	$ 912,146,000