Equity Activity - Reclassifications and Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	$ 9,525	$ 9,649
SG&A expense	5,174	5,955
Other (income) and expense	362	182
Interest expense	280	326
Provision for/(benefit from) income taxes	(51)	(1,226)
Net (income) loss	(955)	(1,175)
Other comprehensive income/(loss)	1,080	(686)
Services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	7,775	7,843
Sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	1,585	1,624
Financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	165	181
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	475	(1,174)
Reclassification/amortization, Net of Tax Amount	606	488
Other comprehensive income/(loss), Before Tax Amount	1,586	(427)
Other comprehensive income/(loss), Tax (Expense)/Benefit	(505)	(260)
Other comprehensive income/(loss)	1,080	(686)
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	321	(1,041)
Other comprehensive income/(loss), Before Tax Amount	549	(919)
Other comprehensive income/(loss), Tax (Expense)/Benefit	(228)	(122)
Other comprehensive income/(loss)	321	(1,041)
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	0	0
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	0	0
Unrealized gains/(losses) arising during the period, Net of Tax Amount	0	0
Other comprehensive income/(loss), Before Tax Amount	0	0
Other comprehensive income/(loss), Tax (Expense)/Benefit	0	0
Other comprehensive income/(loss)	0	0
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	187	(180)
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	(47)	45
Unrealized gains/(losses) arising during the period, Net of Tax Amount	140	(135)
Reclassification/amortization, Net of Tax Amount	119	68
Other comprehensive income/(loss), Before Tax Amount	347	(90)
Other comprehensive income/(loss), Tax (Expense)/Benefit	(88)	23
Other comprehensive income/(loss)	259	(67)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications
Reclassifications and Taxes Related to Items of Other Comprehensive Income
SG&A expense	15	(10)
Other (income) and expense	116	89
Interest expense	16	22
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	(14)	(10)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	22	(9)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	6	8
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	3	2
Net (income) loss	(10)	(7)
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	(6)	2
Net (income) loss	16	(6)
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)	(2)
Net (income) loss	4	6
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	(4)	2
Net (income) loss	11	(7)
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	(29)	(22)
Net (income) loss	87	67
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	(4)	(5)
Net (income) loss	12	16
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	14	3
Reclassification/amortization, Net of Tax Amount	486	419
Other comprehensive income/(loss), Before Tax Amount	689	582
Other comprehensive income/(loss), Tax (Expense)/Benefit	(189)	(160)
Other comprehensive income/(loss)	500	422
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	0	(4)
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	3	1
Reclassification/amortization, Tax (Expense)/Benefit	0	1
Reclassification/amortization, Net of Tax Amount	3	1
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	20	8
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	(6)	(2)
Unrealized gains/(losses) arising during the period, Net of Tax Amount	14	6
Reclassification/amortization, Before Tax Amount	648	570
Reclassification/amortization, Tax (Expense)/Benefit	(177)	(157)
Reclassification/amortization, Net of Tax Amount	471	412
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	17	8
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	(5)	(3)
Unrealized gains/(losses) arising during the period, Net of Tax Amount	$ 12	$ 6