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Financial Instruments - Derivatives, Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	$ (94)	$ (69)	$ 283	$ (377)
Gain (loss) recognized in earnings attributable to risk being hedged	0	66	(133)	327
Cash flow hedges and net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	(4)	40	(491)	375
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	(488)	(28)	(418)	(408)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	27	18	57	49
Interest rate contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI			(168)
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	(439)	(46)	(630)	(134)
Foreign exchange contracts \| Instruments in net investment hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	435	86	306	509
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	22	1	52	29
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	10	8	40	(15)
Cost of financing \| Interest rate contracts \| Derivative instruments in fair value hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	3	(27)	51	(138)
Gain (loss) recognized in earnings attributable to risk being hedged	0	33	(44)	170
Cost of financing \| Interest rate contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	(1)		(2)
Cost of financing \| 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	(20)	(18)	(71)	(56)
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	7	9	19	26
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	11	7	45	(14)
SG&A expense \| Equity contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	9	40	153	38
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	(447)	(8)	(331)	(301)
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	(114)	(55)	(27)	(148)
Interest expense \| Interest rate contracts \| Derivative instruments in fair value hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in earnings on derivatives	9	(26)	105	(128)
Gain (loss) recognized in earnings attributable to risk being hedged	0	33	(89)	157
Interest expense \| Interest rate contracts \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	(3)		(5)
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	(61)	(18)	(146)	(52)
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	$ 20	$ 9	$ 38	$ 24