CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Assets
Cash and due from banks	$ 22,240	$ 20,900	$ 21,880	$ 32,108
Cash and due from banks—intercompany	0	0
Federal funds sold and securities borrowed or purchased under agreements to resell, at fair value	225,093	219,675
Federal funds sold and resale agreements—intercompany	0	0
Trading account assets	273,747	249,956
Trading account assets—intercompany	0	0
Investments	353,252	342,955
Loans, net of unearned income	618,824	617,617
Loans, net of unearned income—intercompany	0	0
Allowance for loan losses	(12,712)	(12,626)	(14,598)	$ (15,994)
Total loans, net	606,112	604,991
Advances to subsidiaries	0	0
Investments in subsidiaries	0	0
Other assets	320,523	292,733
Other assets—intercompany	0	0
Total assets	1,800,967	1,731,210
Liabilities and equity
Deposits	934,591	907,887
Deposits—intercompany	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase, at fair value	157,208	146,496
Federal funds purchased and securities loaned or sold—intercompany	0	0
Trading account liabilities	136,146	117,512
Trading account liabilities—intercompany	0	0
Short-term borrowings, at fair value	20,893	21,079
Short-term borrowings—intercompany	0	0
Long-term debt, at fair value	207,835	201,275
Long-term debt—intercompany	0	0
Advances from subsidiaries	0	0
Other liabilities	115,533	113,869
Other liabilities, intercompany	0	0
Stockholders' equity	228,761	223,092	$ 216,023
Total liabilities and equity	1,800,967	1,731,210
Other	121,621	125,002
Citigroup Inc.
Liabilities and equity
Long-term debt, at fair value	149,140	142,157
Citibank, N.A.
Liabilities and equity
Other	22,800	21,800
Reportable legal entities | Citigroup Inc.
Assets
Cash and due from banks	0	0
Cash and due from banks—intercompany	363	124
Federal funds sold and securities borrowed or purchased under agreements to resell, at fair value	0	0
Federal funds sold and resale agreements—intercompany	0	0
Trading account assets	(4)	(8)
Trading account assets—intercompany	759	1,032
Investments	458	484
Loans, net of unearned income	0	0
Loans, net of unearned income—intercompany	0	0
Allowance for loan losses	0	0
Total loans, net	0	0
Advances to subsidiaries	113,515	104,405
Investments in subsidiaries	227,612	221,362
Other assets	26,474	25,819
Other assets—intercompany	62,966	58,207
Total assets	432,143	411,425
Liabilities and equity
Deposits	0	0
Deposits—intercompany	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase, at fair value	0	0
Federal funds purchased and securities loaned or sold—intercompany	185	185
Trading account liabilities	0	0
Trading account liabilities—intercompany	587	1,036
Short-term borrowings, at fair value	45	146
Short-term borrowings—intercompany	0	0
Long-term debt, at fair value	148,892	141,914
Long-term debt—intercompany	0	0
Advances from subsidiaries	42,379	36,453
Other liabilities	3,957	3,560
Other liabilities, intercompany	8,576	6,274
Stockholders' equity	227,522	221,857
Total liabilities and equity	432,143	411,425
Reportable legal entities | CGMHI
Assets
Cash and due from banks	197	592
Cash and due from banks—intercompany	1,871	1,403
Federal funds sold and securities borrowed or purchased under agreements to resell, at fair value	186,860	178,178
Federal funds sold and resale agreements—intercompany	7,479	15,035
Trading account assets	139,392	124,731
Trading account assets—intercompany	1,432	1,765
Investments	355	402
Loans, net of unearned income	1,063	1,068
Loans, net of unearned income—intercompany	0	0
Allowance for loan losses	(4)	(3)
Total loans, net	1,059	1,065
Advances to subsidiaries	0	0
Investments in subsidiaries	0	0
Other assets	40,830	36,860
Other assets—intercompany	44,693	30,737
Total assets	424,168	390,768
Liabilities and equity
Deposits	0	0
Deposits—intercompany	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase, at fair value	133,899	122,459
Federal funds purchased and securities loaned or sold—intercompany	22,679	22,042
Trading account liabilities	79,313	62,386
Trading account liabilities—intercompany	1,290	2,045
Short-term borrowings, at fair value	530	188
Short-term borrowings—intercompany	38,627	34,916
Long-term debt, at fair value	4,025	2,530
Long-term debt—intercompany	48,642	51,171
Advances from subsidiaries	0	0
Other liabilities	54,921	55,482
Other liabilities, intercompany	11,223	10,967
Stockholders' equity	29,019	26,582
Total liabilities and equity	424,168	390,768
Other Citigroup Inc. subsidiaries and eliminations
Assets
Cash and due from banks	22,043	20,308
Cash and due from banks—intercompany	(2,234)	(1,527)
Federal funds sold and securities borrowed or purchased under agreements to resell, at fair value	38,233	41,497
Federal funds sold and resale agreements—intercompany	(7,479)	(15,035)
Trading account assets	134,359	125,233
Trading account assets—intercompany	(2,191)	(2,797)
Investments	352,439	342,069
Loans, net of unearned income	617,761	616,549
Loans, net of unearned income—intercompany	0	0
Allowance for loan losses	(12,708)	(12,623)
Total loans, net	605,053	603,926
Advances to subsidiaries	(113,515)	(104,405)
Investments in subsidiaries	0	0
Other assets	253,219	230,054
Other assets—intercompany	(107,659)	(88,944)
Total assets	1,172,268	1,150,379
Liabilities and equity
Deposits	934,591	907,887
Deposits—intercompany	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase, at fair value	23,309	24,037
Federal funds purchased and securities loaned or sold—intercompany	(22,864)	(22,227)
Trading account liabilities	56,833	55,126
Trading account liabilities—intercompany	(1,877)	(3,081)
Short-term borrowings, at fair value	20,318	20,745
Short-term borrowings—intercompany	(38,627)	(34,916)
Long-term debt, at fair value	54,918	56,831
Long-term debt—intercompany	(48,642)	(51,171)
Advances from subsidiaries	(42,379)	(36,453)
Other liabilities	56,655	54,827
Other liabilities, intercompany	(19,799)	(17,241)
Stockholders' equity	199,832	196,015
Total liabilities and equity	1,172,268	1,150,379
Consolidating adjustments
Assets
Cash and due from banks	0	0
Cash and due from banks—intercompany	0	0
Federal funds sold and securities borrowed or purchased under agreements to resell, at fair value	0	0
Federal funds sold and resale agreements—intercompany	0	0
Trading account assets	0	0
Trading account assets—intercompany	0	0
Investments	0	0
Loans, net of unearned income	0	0
Loans, net of unearned income—intercompany	0	0
Allowance for loan losses	0	0
Total loans, net	0	0
Advances to subsidiaries	0	0
Investments in subsidiaries	(227,612)	(221,362)
Other assets	0	0
Other assets—intercompany	0	0
Total assets	(227,612)	(221,362)
Liabilities and equity
Deposits	0	0
Deposits—intercompany	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase, at fair value	0	0
Federal funds purchased and securities loaned or sold—intercompany	0	0
Trading account liabilities	0	0
Trading account liabilities—intercompany	0	0
Short-term borrowings, at fair value	0	0
Short-term borrowings—intercompany	0	0
Long-term debt, at fair value	0	0
Long-term debt—intercompany	0	0
Advances from subsidiaries	0	0
Other liabilities	0	0
Other liabilities, intercompany	0	0
Stockholders' equity	(227,612)	(221,362)
Total liabilities and equity	(227,612)	(221,362)
Up to 30 days | Citibank, N.A.
Liabilities and equity
Placements with term of less than 30 days	$ 16,800	$ 13,900