Hedging Activities (Summary of Notional Amounts and Respective Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Notional amount	$ 17,041	$ 15,718
Asset derivatives, fair value	255	265
Liability derivatives, fair value	(337)	(374)
Other Liabilities [Member]
Liability derivatives, fair value	(8)	(8)
Foreign Exchange Contracts [Member] | Designated as Hedging Instrument [Member]
Notional amount	376	294
Foreign Exchange Contracts [Member] | Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Asset derivatives, fair value	12	20
Foreign Exchange Contracts [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Asset derivatives, fair value	2	1
Foreign Exchange Contracts [Member] | Not Designated as Hedging Instrument [Member]
Notional amount	1,136	599
Foreign Exchange Contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Asset derivatives, fair value	9	2
Foreign Exchange Contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Accrued Liabilities [Member]
Liability derivatives, fair value	(8)	(7)
Interest Rate Contracts [Member] | Designated as Hedging Instrument [Member]
Notional amount	850	550
Interest Rate Contracts [Member] | Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Asset derivatives, fair value	9
Interest Rate Contracts [Member] | Designated as Hedging Instrument [Member] | Other Accrued Liabilities [Member]
Liability derivatives, fair value	(2)
Translated Earnings Contracts [Member] | Not Designated as Hedging Instrument [Member]
Notional amount	14,679	14,275
Translated Earnings Contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Asset derivatives, fair value	159	176
Translated Earnings Contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Assets [Member]
Asset derivatives, fair value	64	66
Translated Earnings Contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Accrued Liabilities [Member]
Liability derivatives, fair value	(40)	(34)
Translated Earnings Contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Liability derivatives, fair value	$ (279)	$ (325)