INTEREST INCOME AND EXPENSE (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Interest income
Loan interest, including fees		$ 15,393	$ 15,805	$ 45,083	$ 46,829
Deposits with banks		3,435	3,050	9,479	8,407
Securities borrowed and purchased under agreements to resell		7,003	7,293	19,915	22,326
Investments, including dividends		4,170	4,683	12,542	14,353
Trading account assets		5,289	4,451	15,480	13,082
Other interest-earning assets		1,400	1,174	3,716	3,669
Total interest income	[1]	36,690	36,456	106,215	108,666
Interest expense
Deposits		9,163	10,319	26,286	30,965
Securities loaned and sold under agreements to repurchase		7,356	7,328	20,550	21,256
Trading account liabilities		755	792	2,260	2,417
Short-term borrowings and other interest-bearing liabilities		1,933	2,009	5,459	5,873
Long-term debt		2,543	2,646	7,533	7,793
Total interest expense	[1]	21,750	23,094	62,088	68,304
Net interest income	[1]	14,940	13,362	44,127	40,362
Provision for credit losses on loans		2,259	2,382	7,297	7,163
Net interest income after provision for credit losses on loans		12,681	10,980	36,830	33,199
Consumer loans
Interest income
Loan interest, including fees		10,150	10,051	29,679	29,629
Corporate loans
Interest income
Loan interest, including fees		$ 5,243	$ 5,754	$ 15,404	$ 17,200

[1] Effective January 1, 2025, certain transaction processing fees paid by Citi, primarily to credit card networks, which were previously presented within Other operating expenses, are presented as contra-revenue within Commissions and fees reported in Non-interest revenue. Prior periods were conformed to reflect this change in presentation.