Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative Asset, Notional Amount	$ 17,041	$ 15,718
Gross Notional Value, Translated Earnings Contracts [Member]
Derivative Asset, Notional Amount	14,700	14,300
Gross Notional Value, Collar Options [Member]
Derivative Asset, Notional Amount	2,600	1,300
Gross Notional Value, Foreign Exchange Forward [Member]
Derivative Asset, Notional Amount	12,100	13,000
Gross Notional Value, Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member]
Derivative Asset, Notional Amount	$ 9,700	$ 11,700