SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Assets and Liabilities of VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Cash	$ 25,763		$ 30,577	$ 24,902
Trading account assets	423,189		334,114
Investments	507,145		526,582
Loans, net of unearned income	660,612		657,221
Allowance for credit losses on loans (ACLL)	(17,496)	$ (17,169)	(16,974)	(15,952)	$ (15,393)	$ (16,455)
Total loans, net	643,116		640,247
Other assets, at fair value	102,972		103,743
Total assets	2,423,675		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	40,430		47,096
Long-term debt	274,510		271,606
Other liabilities, plus allowances	79,314		87,873
Total liabilities	2,214,253		2,214,838
Consumer
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	374,591		368,067
Allowance for credit losses on loans (ACLL)	(14,866)	(14,389)	(14,119)	(12,983)	(12,368)	(14,040)
Corporate
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	286,021		289,154
Allowance for credit losses on loans (ACLL)	(2,630)	$ (2,780)	(2,855)	$ (2,969)	$ (3,025)	$ (2,415)
Consolidated VIEs
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Cash	69		61
Trading account assets	10,417		9,153
Investments	496		594
Loans, net of unearned income	53,517		54,808
Allowance for credit losses on loans (ACLL)	(2,623)		(2,520)
Total loans, net	50,894		52,288
Other assets, at fair value	120		105
Total assets	61,996		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	9,652		9,807
Long-term debt	7,930		10,324
Other liabilities, plus allowances	853		622
Total liabilities	18,435		20,753
Consolidated VIEs | Consumer
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	34,786		35,026
Consolidated VIEs | Corporate
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	$ 18,731		$ 19,782