Equity Activity - Reclassifications and Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	$ 9,741	$ 9,423	$ 19,266	$ 19,071
SG&A expense	5,334	5,248	10,508	11,203
Other (income) and expense	315	179	676	361
Interest expense	281	323	562	649
Provision for/(benefit from) income taxes	227	209	177	(1,017)
Net (income) loss	(1,325)	(1,361)	(2,280)	(2,536)
Other comprehensive income/(loss)	605	527	1,685	(160)
Services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	7,871	7,520	15,646	15,363
Sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	1,694	1,739	3,279	3,363
Financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	176	165	341	345
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			532	(1,025)
Reclassification/amortization, Net of Tax Amount			1,153	866
Other comprehensive income/(loss), Before Tax Amount	745	548	2,330	121
Other comprehensive income/(loss), Tax (Expense)/Benefit	(140)	(21)	(645)	(281)
Other comprehensive income/(loss)	605	527	1,685	(160)
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			393	(902)
Other comprehensive income/(loss), Before Tax Amount	28	4	577	(915)
Other comprehensive income/(loss), Tax (Expense)/Benefit	44	135	(184)	13
Other comprehensive income/(loss)	72	139	393	(902)
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	1	0	1
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	0	0	0	0
Unrealized gains/(losses) arising during the period, Net of Tax Amount	0	1	0	1
Other comprehensive income/(loss), Before Tax Amount	0	1	0	1
Other comprehensive income/(loss), Tax (Expense)/Benefit	0	0	0	0
Other comprehensive income/(loss)	0	1	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	(34)	(36)	153	(216)
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	9	9	(39)	55
Unrealized gains/(losses) arising during the period, Net of Tax Amount	(26)	(26)	114	(162)
Reclassification/amortization, Net of Tax Amount			187	25
Other comprehensive income/(loss), Before Tax Amount	56	(94)	404	(184)
Other comprehensive income/(loss), Tax (Expense)/Benefit	(14)	25	(102)	47
Other comprehensive income/(loss)	42	(70)	301	(137)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications
Reclassifications and Taxes Related to Items of Other Comprehensive Income
SG&A expense	16	(7)	31	(17)
Other (income) and expense	49	(70)	165	19
Interest expense	16	19	31	41
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Services
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	(7)	1	(21)	(9)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Sales
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	10	(9)	32	(18)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Reclassifications | Financing
Reclassifications and Taxes Related to Items of Other Comprehensive Income
Cost	6	7	12	15
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	0	5	2
Net (income) loss	(5)	1	(16)	(6)
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	(3)	3	(8)	5
Net (income) loss	8	(7)	24	(13)
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	(1)	(2)	(3)	(4)
Net (income) loss	4	5	9	11
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	(8)	4
Net (income) loss	12	(5)	23	(13)
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	(12)	18	(41)	(5)
Net (income) loss	37	(52)	123	15
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)	(8)	(10)
Net (income) loss	12	15	24	31
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			25	38
Reclassification/amortization, Net of Tax Amount			966	841
Other comprehensive income/(loss), Before Tax Amount	661	637	1,350	1,219
Other comprehensive income/(loss), Tax (Expense)/Benefit	(170)	(180)	(359)	(341)
Other comprehensive income/(loss)	491	457	991	879
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		0	(4)
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	0	0	0	1
Unrealized gains/(losses) arising during the period, Net of Tax Amount	0	0	0	(3)
Reclassification/amortization, Before Tax Amount	1	0	4	1
Reclassification/amortization, Tax (Expense)/Benefit	1	1	0	1
Reclassification/amortization, Net of Tax Amount	1	1	4	2
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	2	57	22	65
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	10	(22)	4	(24)
Unrealized gains/(losses) arising during the period, Net of Tax Amount	11	35	25	41
Reclassification/amortization, Before Tax Amount	643	566	1,291	1,136
Reclassification/amortization, Tax (Expense)/Benefit	(175)	(155)	(352)	(312)
Reclassification/amortization, Net of Tax Amount	467	411	938	824
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	16	13	34	21
Unrealized gains/(losses) arising during the period, Tax (Expense)/Benefit	(5)	(4)	(10)	(6)
Unrealized gains/(losses) arising during the period, Net of Tax Amount	$ 11	$ 9	$ 23	$ 15