DISCONTINUED OPERATIONS, SIGNIFICANT DISPOSALS AND OTHER BUSINESS EXITS - Summarized Reserve Charges (Details) - Citibank Korea Inc. - Employee Severance $ in Millions	2 Months Ended
Dec. 31, 2021 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Voluntary termination benefits and related costs	$ 1,100
Original reserve charges	1,052
Utilization	(1)
Foreign exchange	3
Balance at December 31, 2021	$ 1,054

Restructuring and Related Charges, Initial Charges in Reserve

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Restructuring and Related Charges, Pre-Tax

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Restructuring and Related Charges, Utilization

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Amount of foreign currency translation gain (loss) which decreases (increases) the restructuring reserve.

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