Financial Instruments - Derivatives, Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	$ (10)	$ 34	$ 233	$ 830
Gain (loss) recognized in earnings attributable to risk being hedged	41	83	42	(267)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Recognized in OCI	(577)	(96)	(1,712)	(1,292)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Reclassified from AOCI to Earnings	73	(15)	347	(26)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, (Ineffectiveness) and Amounts Excluded from Effectiveness Testing	7	24	37	49
Gain (loss) on fair value hedges ineffectiveness		(3)
Gains (losses) excluded from the assessment of hedge effectiveness for fair value hedges
Gains (losses) associated with underlying exposure that did not occur or was not expected to occur for cash flow hedges
Maximum
Derivative Instruments, Gain (Loss)
Gain (loss) on fair value hedges ineffectiveness	(1)		(1)	1
Foreign exchange contracts \| Derivative instruments in cash flow hedging relationships
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Recognized in OCI	(70)	35	(198)	(221)
Foreign exchange contracts \| Net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Recognized in OCI	(507)	(131)	(1,513)	(1,071)
Cost of financing \| Interest rate contracts \| Derivative instruments in fair value hedging relationships
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	(3)	(20)	37	195
Gain (loss) recognized in earnings attributable to risk being hedged	20	40	22	(127)
Cost of financing \| Foreign exchange contracts \| Net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, (Ineffectiveness) and Amounts Excluded from Effectiveness Testing	0		0
Interest expense \| Interest rate contracts \| Derivative instruments in fair value hedging relationships
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	(3)	(21)	34	214
Gain (loss) recognized in earnings attributable to risk being hedged	20	43	20	(140)
Interest expense \| Interest rate contracts \| Derivative instruments in cash flow hedging relationships
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Reclassified from AOCI to Earnings	(7)	(7)	(21)	(17)
Interest expense \| Foreign exchange contracts \| Net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, (Ineffectiveness) and Amounts Excluded from Effectiveness Testing	8	25	34	51
SG&A expense \| Foreign exchange contracts \| Derivative instruments in cash flow hedging relationships
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Reclassified from AOCI to Earnings	(6)	2	23	(1)
SG&A expense \| Equity contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	31	45	88	87
Other (income) and expense \| Interest rate contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives		0		0
Other (income) and expense \| Foreign exchange contracts \| Derivative instruments in cash flow hedging relationships
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Reclassified from AOCI to Earnings	64	(6)	275	6
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, (Ineffectiveness) and Amounts Excluded from Effectiveness Testing	(1)	(1)	2	(1)
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	(35)	30	74	335
Other (income) and expense \| Equity contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives		0		(1)
Cost of sales \| Foreign exchange contracts \| Derivative instruments in cash flow hedging relationships
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Reclassified from AOCI to Earnings	1	(7)	23	(5)
Cost of services \| Foreign exchange contracts \| Derivative instruments in cash flow hedging relationships
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income, Effective Portion Reclassified from AOCI to Earnings	$ 20	$ 3	$ 47	$ (9)

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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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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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

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