Bank Financing and Debt (Schedule of Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Commercial paper	$ 0	$ 674
Senior debt (2.30% - 7.875% due 2019 - 2045)	9,328	9,435
Obligations under finance leases	41	43
Total debt	9,369	10,152
Less commercial paper	0	674
Less current portion of long-term debt	11	13
Total long-term debt, net of current portion	9,358	9,465
Senior Debt [Member]
Debt Instrument [Line Items]
Net unamortized discount on senior debt	61	58
Unamortized deferred financing costs	45	43
Decrease to carrying value of debt relating to previously settled fair value hedges	7	5
Face value of debt	$ 9,440	$ 9,540
Senior Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	2.30%
Senior Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate	7.875%

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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