RELATED PARTY TRANSACTIONS - Related Party Revenue and Purchases (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Revenues		$ 704	$ 645	$ 613
related-party cost of services		3,979	3,767	3,592
Cost of services		16,550	17,137	17,676
Depreciation		1,300	1,445	1,469
Payment for purchase of hardware from IBM		752	1,036	1,190
IBM
Related Party Transaction [Line Items]
Revenues		704	645	613
IBM \| Outsourcing
Related Party Transaction [Line Items]
Cost of services	$ 312
IBM \| Networking and IT services
Related Party Transaction [Line Items]
Cost of services		384	509	484
IBM \| Hardware, software and services
Related Party Transaction [Line Items]
Cost of services		2,800	2,700	2,600
Depreciation		447	520	538
Payment for purchase of hardware from IBM		299	504	526
Due from related party	$ 265	$ 265
Upgraded hardware period		2 years
Estimated useful lives (in years)		5 years
IBM \| Cost of service
Related Party Transaction [Line Items]
related-party cost of services		$ 4,000	$ 3,800	$ 3,600

Period of time in which a related party will continue to provide hardware upgrades at no cost.

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The aggregate cost of goods produced and sold and services rendered during the reporting period.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Direct costs arising from transactions with related parties who are not affiliates or joint Ventures. These costs are categorized as cost of goods sold.

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Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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