BASIS OF PRESENTATION, UPDATED ACCOUNTING POLICIES AND ACCOUNTING CHANGES - Accounting Changes (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended
		Jan. 31, 2023	Mar. 31, 2023		Jun. 30, 2022	Mar. 31, 2022		Dec. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			$ (17,169)			$ (15,393)		$ (16,974)	$ (16,455)
Other assets, at fair value			103,522					103,743
Stockholders’ equity			209,019			198,353		201,838
Transfer of investment securities from HTM to AFS, amortized cost		$ 3,300
Transfer of investment securities from HTM to AFS, fair value		3,400	3,324	[1],[2],[3]		0	[1],[2],[3]
Transfer of securities from HTM to AFS, unrealized gain		$ 100
Other liabilities			(76,365)					(87,873)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses								352	0
Other assets, at fair value								44
Deferred tax assets								106
Other liabilities								39
Macroeconomic Uncertainty
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in allowance for credit losses					$ 800
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders’ equity			198,353			187,962		194,734	184,948
Retained earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders’ equity	[4]							290	0
Accumulated other comprehensive income (loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders’ equity			$ (45,441)			$ (43,585)		(47,062)	(38,765)
Accumulated other comprehensive income (loss) | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders’ equity	[4]							$ 27	$ 0
Change in Accounting Method Accounted for as Change in Estimate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in allowance for credit losses					$ (300)

[1] In January 2023, Citi adopted ASU 2022-01. Upon adoption, Citi transferred $3.3 billion of mortgage-backed securities from HTM classification to AFS classification as allowed under the ASU. At the time of transfer, the securities were in an unrealized gain position of $0.1 billion, which was recorded in AOCI upon transfer. See Note 1.

[2] Operating and finance lease right-of-use assets and lease liabilities represent non-cash investing and financing activities, respectively, and are not included in the non-cash investing activities presented here. See Note 24 for more information and balances as of March 31, 2023.

[3] See Note 2 for further information on significant disposals.

[4] See Note 1 for additional details.