Equity Activity - Reclassifications and Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	$ 9,130	$ 9,692	$ 28,202	$ 29,982
SG&A expense	4,647	5,024	15,849	15,171
Other (income) and expense	253	(31)	614	(850)
Interest expense	323	432	971	990
Provision for/(benefit from) income taxes	128	(151)	(888)	407
Net (income) loss	(1,698)	(1,672)	(4,234)	(5,761)
Other comprehensive income/(loss)	172	(245)	12	404
Services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	7,357	7,840	22,720	24,293
Sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	1,601	1,635	4,964	4,979
Financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	172	217	517	710
Accumulated Other Comprehensive Income/(Loss)
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Net of Tax Amount			(1,242)	(916)
Reclassification/amortization, Net of Tax Amount			1,255	1,320
Other comprehensive income/(loss), Before Tax Amount	66	4	187	784
Other comprehensive income/(loss), Tax (Expense)/Benefit	106	(249)	(175)	(380)
Other comprehensive income/(loss)	172	(245)	12	404
Foreign Currency Translation Adjustments
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Net of Tax Amount			(1,094)	(405)
Other comprehensive income/(loss), Before Tax Amount	(439)	(509)	(1,354)	(333)
Other comprehensive income/(loss), Tax (Expense)/Benefit	247	(109)	260	(72)
Other comprehensive income/(loss)	(192)	(618)	(1,094)	(405)
Net Unrealized Gains/(Losses) on Available-For-Sale Securities
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Before Tax Amount	(1)	3	0	1
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	0	(1)	0	0
Unrealized gains/(losses) arising during the period, Net of Tax Amount	(1)	2	0	1
Other comprehensive income/(loss), Before Tax Amount	(1)	3	0	1
Other comprehensive income/(loss), Tax (Expense)/Benefit	0	(1)	0	0
Other comprehensive income/(loss)	(1)	2	0	1
Net Unrealized Gains/(Losses) on Cash Flow Hedges
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Before Tax Amount	(32)	(439)	(249)	(798)
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	8	110	63	196
Unrealized gains/(losses) arising during the period, Net of Tax Amount	(24)	(329)	(186)	(601)
Reclassification/amortization, Net of Tax Amount			(27)	315
Other comprehensive income/(loss), Before Tax Amount	(101)	49	(285)	(380)
Other comprehensive income/(loss), Tax (Expense)/Benefit	26	(12)	73	93
Other comprehensive income/(loss)	(75)	36	(212)	(287)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications
Reclassifications and Taxes Related to Items of Other Comprehensive Income
SG&A expense	5	(11)	(12)	(45)
Other (income) and expense	(93)	447	(74)	331
Interest expense	19	64	60	150
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	(10)	(22)	(18)	(52)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	4	(10)	(14)	(40)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	6	21	21	73
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Cost of services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Provision for/(benefit from) income taxes	2	6	5	13
Net (income) loss	(7)	(17)	(14)	(38)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Cost of sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Provision for/(benefit from) income taxes	(1)	3	4	11
Net (income) loss	3	(7)	(10)	(29)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Cost of financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Provision for/(benefit from) income taxes	(2)	(5)	(5)	(18)
Net (income) loss	5	15	16	55
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | SG&A expense
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Provision for/(benefit from) income taxes	(1)	3	3	12
Net (income) loss	4	(8)	(9)	(33)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Other (income) and expense
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Provision for/(benefit from) income taxes	23	(112)	19	(83)
Net (income) loss	(70)	334	(55)	248
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Interest expense
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Provision for/(benefit from) income taxes	(5)	(16)	(15)	(38)
Net (income) loss	14	48	45	112
Net Change Retirement-Related Benefit Plans
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Net of Tax Amount			37	89
Reclassification/amortization, Net of Tax Amount			1,281	1,005
Other comprehensive income/(loss), Before Tax Amount	607	461	1,826	1,496
Other comprehensive income/(loss), Tax (Expense)/Benefit	(167)	(127)	(507)	(401)
Other comprehensive income/(loss)	440	335	1,319	1,095
Retirement-Related Benefit Plans, Prior Service Costs/(Credits)
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Before Tax Amount	(1)		(5)
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	0		1
Unrealized gains/(losses) arising during the period, Net of Tax Amount	0		(3)
Reclassification/amortization, Before Tax Amount	0	(3)	1	(9)
Reclassification/amortization, Tax (Expense)/Benefit	1	3	2	4
Reclassification/amortization, Net of Tax Amount	1	(1)	3	(5)
Retirement-Related Benefit Plans, Net Gains/(Losses)
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Before Tax Amount	0	0	65	113
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	0	0	(24)	(23)
Unrealized gains/(losses) arising during the period, Net of Tax Amount	0	0	41	90
Reclassification/amortization, Before Tax Amount	586	461	1,722	1,385
Reclassification/amortization, Tax (Expense)/Benefit	(161)	(128)	(473)	(380)
Reclassification/amortization, Net of Tax Amount	425	333	1,249	1,005
Retirement-Related Benefit Plans, Curtailments and Settlements
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Unrealized gains/(losses) arising during the period, Before Tax Amount	21	3	42	7
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	(6)	(1)	(12)	(1)
Unrealized gains/(losses) arising during the period, Net of Tax Amount	$ 14	$ 2	$ 30	$ 6