SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Assets and Liabilities of VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Cash	$ 26,224	$ 30,577	$ 27,768
Trading account assets	383,906	334,114
Investments	512,578	526,582
Loans, net of unearned income	651,995	657,221
Allowance for credit losses on loans (ACLL)	(17,169)	(16,974)	(15,393)	$ (16,455)
Total loans, net	634,826	640,247
Other assets, at fair value	103,522	103,743
Total assets	2,455,113	2,416,676
Liabilities of consolidated VIEs for which creditors or beneficial interest holders do not have recourse to the general credit of Citigroup
Short-term borrowings, at fair value	40,187	47,096
Long-term debt	279,684	271,606
Other liabilities, plus allowances	76,365	87,873
Total liabilities	2,246,094	2,214,838
Consumer
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	363,696	368,067
Allowance for credit losses on loans (ACLL)	(14,389)	(14,119)	(12,368)	(14,040)
Corporate
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	288,299	289,154
Allowance for credit losses on loans (ACLL)	(2,780)	(2,855)	$ (3,025)	$ (2,415)
Consolidated VIEs
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Cash	58	61
Trading account assets	9,921	9,153
Investments	614	594
Loans, net of unearned income	52,763	54,808
Allowance for credit losses on loans (ACLL)	(2,572)	(2,520)
Total loans, net	50,191	52,288
Other assets, at fair value	113	105
Total assets	60,897	62,201
Liabilities of consolidated VIEs for which creditors or beneficial interest holders do not have recourse to the general credit of Citigroup
Short-term borrowings, at fair value	9,673	9,807
Long-term debt	9,572	10,324
Other liabilities, plus allowances	854	622
Total liabilities	20,099	20,753
Consolidated VIEs | Consumer
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	33,188	35,026
Consolidated VIEs | Corporate
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	$ 19,575	$ 19,782