Financial Instruments - Derivatives, Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	$ (69)	$ (10)	$ (377)	$ 233
Gain (loss) recognized in earnings attributable to risk being hedged	66	41	327	42
Gains (losses) excluded from the assessment of hedge effectiveness for fair value hedges
Gains (losses) excluded from the assessment of hedge effectiveness for cash value hedges
Gains (losses) associated with underlying exposure that did not occur or was not expected to occur for cash flow hedges
Cash flow hedges and net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	40	(577)	375	(1,712)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	(28)	73	(408)	347
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	18	7	49	37
Foreign exchange contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	(46)	(70)	(134)	(198)
Foreign exchange contracts \| Instruments in net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	86	(507)	509	(1,513)
Cost of financing \| Interest rate contracts \| Derivative instruments in fair value hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	(27)	(3)	(138)	37
Gain (loss) recognized in earnings attributable to risk being hedged	33	20	170	22
Cost of financing \| Foreign exchange contracts \| Instruments in net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	8	0	24	0
Interest expense \| Interest rate contracts \| Derivative instruments in fair value hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	(26)	(3)	(128)	34
Gain (loss) recognized in earnings attributable to risk being hedged	33	20	157	20
Interest expense \| Foreign exchange contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	(36)	(7)	(108)	(21)
Interest expense \| Foreign exchange contracts \| Instruments in net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	9	8	25	34
Other (Income) and Expense \| Foreign exchange contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	(8)	64	(301)	275
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing		(1)		2
Other (Income) and Expense \| Foreign exchange contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	(55)	(35)	(148)	74
Cost of Sales \| Foreign exchange contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	8	1	(15)	23
Cost of Services \| Foreign exchange contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	1	20	29	47
SG&A Expense \| Foreign exchange contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	7	(6)	(14)	23
SG&A Expense \| Equity contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	$ 40	$ 31	$ 38	$ 88

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of gain (loss) from excluded component of derivative hedge, recognized in earnings. Excludes recognition under systematic and rational method.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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The net gain (loss) relating to components of the gain (loss) on the cash flow hedging instrument excluded from the assessment of cash flow hedge effectiveness. Recognized in earnings.

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Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

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The amount of net gain (loss) reclassified into earnings in the period when cash flow hedge is discontinued because it is probable that the original forecasted transactions will not occur by the end of the original period or an additional two month time period.

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