CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Assets
Cash and due from banks	$ 27,768	$ 27,515
Cash and due from banks—intercompany	0	0
Deposits with banks, net of allowance	244,319	234,518
Deposits with banks—intercompany	0	0
Securities borrowed and purchased under resale agreements	345,410	327,288
Securities borrowed and purchased under resale agreements—intercompany	0	0
Trading account assets	357,997	331,945
Trading account assets—intercompany	0	0
Investments	514,602	512,822
Loans, net of unearned income	659,669	667,767
Loans, net of unearned income—intercompany	0	0
Allowance for credit losses on loans (ACLL)	(15,393)	(16,455)	$ (21,638)	$ (24,956)
Total loans, net	644,276	651,312
Advances to subsidiaries	0	0
Investments in subsidiaries	0	0
Other assets, net of allowance	259,733	206,013
Other assets—intercompany	0	0
Total assets	2,394,105	2,291,413	2,291,000
Liabilities and equity
Deposits	1,333,711	1,317,230
Deposits—intercompany	0	0
Securities loaned and sold under repurchase agreements	204,494	191,285
Securities loaned and sold under repurchase agreements—intercompany	0	0
Trading account liabilities	188,059	161,529
Trading account liabilities—intercompany	0	0
Short-term borrowings	30,144	27,973
Short-term borrowings—intercompany	0	0
Long-term debt	253,954	254,374
Long-term debt—intercompany	0	0
Advances from subsidiaries	0	0
Other liabilities	185,390	136,350
Other liabilities—intercompany	0	0
Stockholders’ equity	198,353	202,672	$ 203,273
Total liabilities and equity	2,394,105	2,291,413
Increase in other assets	146,128	125,879
Citigroup parent company
Liabilities and equity
Long-term debt	170,142	164,945
Citibank, N.A.
Liabilities and equity
Increase in other assets	32,800	30,500
Citibank, N.A. | Up to 30 days
Liabilities and equity
Placements with term of less than 30 days	20,600	19,500
Reportable legal entities | Citigroup parent company
Assets
Cash and due from banks	0	0
Cash and due from banks—intercompany	22	17
Deposits with banks, net of allowance	0	0
Deposits with banks—intercompany	3,500	3,500
Securities borrowed and purchased under resale agreements	0	0
Securities borrowed and purchased under resale agreements—intercompany	0	0
Trading account assets	237	248
Trading account assets—intercompany	421	1,215
Investments	1	1
Loans, net of unearned income	0	0
Loans, net of unearned income—intercompany	0	0
Allowance for credit losses on loans (ACLL)	0	0
Total loans, net	0	0
Advances to subsidiaries	151,425	142,144
Investments in subsidiaries	222,123	223,303
Other assets, net of allowance	10,722	10,589
Other assets—intercompany	4,109	2,737
Total assets	392,560	383,754
Liabilities and equity
Deposits	0	0
Deposits—intercompany	0	0
Securities loaned and sold under repurchase agreements	0	0
Securities loaned and sold under repurchase agreements—intercompany	0	0
Trading account liabilities	22	17
Trading account liabilities—intercompany	282	777
Short-term borrowings	0	0
Short-term borrowings—intercompany	0	0
Long-term debt	170,142	164,945
Long-term debt—intercompany	0	0
Advances from subsidiaries	21,999	13,469
Other liabilities	2,289	2,574
Other liabilities—intercompany	117	0
Stockholders’ equity	197,709	201,972
Total liabilities and equity	392,560	383,754
Reportable legal entities | CGMHI
Assets
Cash and due from banks	627	834
Cash and due from banks—intercompany	7,857	6,890
Deposits with banks, net of allowance	7,994	7,936
Deposits with banks—intercompany	10,709	11,005
Securities borrowed and purchased under resale agreements	288,195	269,608
Securities borrowed and purchased under resale agreements—intercompany	20,795	23,362
Trading account assets	207,204	189,841
Trading account assets—intercompany	1,491	1,438
Investments	233	224
Loans, net of unearned income	2,716	2,293
Loans, net of unearned income—intercompany	0	0
Allowance for credit losses on loans (ACLL)	0	0
Total loans, net	2,716	2,293
Advances to subsidiaries	0	0
Investments in subsidiaries	0	0
Other assets, net of allowance	91,083	69,312
Other assets—intercompany	63,590	60,567
Total assets	702,494	643,310
Liabilities and equity
Deposits	0	0
Deposits—intercompany	0	0
Securities loaned and sold under repurchase agreements	184,433	171,818
Securities loaned and sold under repurchase agreements—intercompany	54,802	62,197
Trading account liabilities	127,702	122,383
Trading account liabilities—intercompany	326	500
Short-term borrowings	16,583	13,425
Short-term borrowings—intercompany	18,851	17,230
Long-term debt	63,195	61,416
Long-term debt—intercompany	83,099	76,335
Advances from subsidiaries	0	0
Other liabilities	91,625	68,206
Other liabilities—intercompany	22,671	11,774
Stockholders’ equity	39,207	38,026
Total liabilities and equity	702,494	643,310
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Assets
Cash and due from banks	27,141	26,681
Cash and due from banks—intercompany	(7,879)	(6,907)
Deposits with banks, net of allowance	236,325	226,582
Deposits with banks—intercompany	(14,209)	(14,505)
Securities borrowed and purchased under resale agreements	57,215	57,680
Securities borrowed and purchased under resale agreements—intercompany	(20,795)	(23,362)
Trading account assets	150,556	141,856
Trading account assets—intercompany	(1,912)	(2,653)
Investments	514,368	512,597
Loans, net of unearned income	656,953	665,474
Loans, net of unearned income—intercompany	0	0
Allowance for credit losses on loans (ACLL)	(15,393)	(16,455)
Total loans, net	641,560	649,019
Advances to subsidiaries	(151,425)	(142,144)
Investments in subsidiaries	0	0
Other assets, net of allowance	157,928	126,112
Other assets—intercompany	(67,699)	(63,304)
Total assets	1,521,174	1,487,652
Liabilities and equity
Deposits	1,333,711	1,317,230
Deposits—intercompany	0	0
Securities loaned and sold under repurchase agreements	20,061	19,467
Securities loaned and sold under repurchase agreements—intercompany	(54,802)	(62,197)
Trading account liabilities	60,335	39,129
Trading account liabilities—intercompany	(608)	(1,277)
Short-term borrowings	13,561	14,548
Short-term borrowings—intercompany	(18,851)	(17,230)
Long-term debt	20,617	28,013
Long-term debt—intercompany	(83,099)	(76,335)
Advances from subsidiaries	(21,999)	(13,469)
Other liabilities	91,476	65,570
Other liabilities—intercompany	(22,788)	(11,774)
Stockholders’ equity	183,560	185,977
Total liabilities and equity	1,521,174	1,487,652
Consolidating adjustments
Assets
Cash and due from banks	0	0
Cash and due from banks—intercompany	0	0
Deposits with banks, net of allowance	0	0
Deposits with banks—intercompany	0	0
Securities borrowed and purchased under resale agreements	0	0
Securities borrowed and purchased under 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 credit losses on loans (ACLL)	0	0
Total loans, net	0	0
Advances to subsidiaries	0	0
Investments in subsidiaries	(222,123)	(223,303)
Other assets, net of allowance	0	0
Other assets—intercompany	0	0
Total assets	(222,123)	(223,303)
Liabilities and equity
Deposits	0	0
Deposits—intercompany	0	0
Securities loaned and sold under repurchase agreements	0	0
Securities loaned and sold under repurchase agreements—intercompany	0	0
Trading account liabilities	0	0
Trading account liabilities—intercompany	0	0
Short-term borrowings	0	0
Short-term borrowings—intercompany	0	0
Long-term debt	0	0
Long-term debt—intercompany	0	0
Advances from subsidiaries	0	0
Other liabilities	0	0
Other liabilities—intercompany	0	0
Stockholders’ equity	(222,123)	(223,303)
Total liabilities and equity	$ (222,123)	$ (223,303)