CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Assets
Cash and due from banks	$ 24,902		$ 27,515
Cash and due from banks—intercompany	0		0
Deposits with banks, net of allowance	259,128		234,518
Deposits with banks—intercompany	0		0
Securities borrowed and purchased under resale agreements	361,334		327,288
Securities borrowed and purchased under resale agreements—intercompany	0		0
Trading account assets	340,875		331,945
Trading account assets—intercompany	0		0
Investments	513,878		512,822
Loans, net of unearned income	657,333		667,767
Loans, net of unearned income—intercompany	0		0
Allowance for credit losses on loans (ACLL)	(15,952)	$ (15,393)	(16,455)	$ (19,238)	$ (21,638)	$ (24,956)
Total loans, net	641,381		651,312
Advances to subsidiaries	0		0
Investments in subsidiaries	0		0
Other assets, net of allowance	239,406		206,013
Other assets—intercompany	0		0
Total assets	2,380,904		2,291,413	2,291,000
Liabilities and equity
Deposits	1,321,848		1,317,230
Deposits—intercompany	0		0
Securities loaned and sold under repurchase agreements	198,472		191,285
Securities loaned and sold under repurchase agreements—intercompany	0		0
Trading account liabilities	180,453		161,529
Trading account liabilities—intercompany	0		0
Short-term borrowings	40,054		27,973
Short-term borrowings—intercompany	0		0
Long-term debt	257,425		254,374
Long-term debt—intercompany	0		0
Advances from subsidiaries	0		0
Other liabilities	183,026		136,350
Other liabilities—intercompany	0		0
Stockholders’ equity	199,626		202,672	$ 202,910
Total liabilities and equity	2,380,904		2,291,413
Increase in other assets	134,797		125,879
Citigroup parent company
Liabilities and equity
Long-term debt	167,874		164,945
Citibank, N.A.
Liabilities and equity
Increase in other assets	36,800		30,500
Citibank, N.A. | Up to 30 days
Liabilities and equity
Placements with term of less than 30 days	27,100		19,500
Reportable legal entities | Citigroup parent company
Assets
Cash and due from banks	0		0
Cash and due from banks—intercompany	14		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	193		248
Trading account assets—intercompany	908		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	142,832		142,144
Investments in subsidiaries	222,196		223,303
Other assets, net of allowance	11,177		10,589
Other assets—intercompany	3,857		2,737
Total assets	384,678		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	29		17
Trading account liabilities—intercompany	141		777
Short-term borrowings	0		0
Short-term borrowings—intercompany	0		0
Long-term debt	167,874		164,945
Long-term debt—intercompany	0		0
Advances from subsidiaries	14,834		13,469
Other liabilities	2,639		2,574
Other liabilities—intercompany	147		0
Stockholders’ equity	199,014		201,972
Total liabilities and equity	384,678		383,754
Reportable legal entities | CGMHI
Assets
Cash and due from banks	1,103		834
Cash and due from banks—intercompany	5,357		6,890
Deposits with banks, net of allowance	8,105		7,936
Deposits with banks—intercompany	10,417		11,005
Securities borrowed and purchased under resale agreements	301,364		269,608
Securities borrowed and purchased under resale agreements—intercompany	19,070		23,362
Trading account assets	191,486		189,841
Trading account assets—intercompany	2,991		1,438
Investments	234		224
Loans, net of unearned income	1,862		2,293
Loans, net of unearned income—intercompany	0		0
Allowance for credit losses on loans (ACLL)	0		0
Total loans, net	1,862		2,293
Advances to subsidiaries	0		0
Investments in subsidiaries	0		0
Other assets, net of allowance	90,338		69,312
Other assets—intercompany	77,889		60,567
Total assets	710,216		643,310
Liabilities and equity
Deposits	0		0
Deposits—intercompany	0		0
Securities loaned and sold under repurchase agreements	179,917		171,818
Securities loaned and sold under repurchase agreements—intercompany	63,380		62,197
Trading account liabilities	114,029		122,383
Trading account liabilities—intercompany	2,624		500
Short-term borrowings	18,372		13,425
Short-term borrowings—intercompany	19,557		17,230
Long-term debt	71,603		61,416
Long-term debt—intercompany	86,144		76,335
Advances from subsidiaries	0		0
Other liabilities	97,035		68,206
Other liabilities—intercompany	17,915		11,774
Stockholders’ equity	39,640		38,026
Total liabilities and equity	710,216		643,310
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Assets
Cash and due from banks	23,799		26,681
Cash and due from banks—intercompany	(5,371)		(6,907)
Deposits with banks, net of allowance	251,023		226,582
Deposits with banks—intercompany	(13,917)		(14,505)
Securities borrowed and purchased under resale agreements	59,970		57,680
Securities borrowed and purchased under resale agreements—intercompany	(19,070)		(23,362)
Trading account assets	149,196		141,856
Trading account assets—intercompany	(3,899)		(2,653)
Investments	513,643		512,597
Loans, net of unearned income	655,471		665,474
Loans, net of unearned income—intercompany	0		0
Allowance for credit losses on loans (ACLL)	(15,952)		(16,455)
Total loans, net	639,519		649,019
Advances to subsidiaries	(142,832)		(142,144)
Investments in subsidiaries	0		0
Other assets, net of allowance	137,891		126,112
Other assets—intercompany	(81,746)		(63,304)
Total assets	1,508,206		1,487,652
Liabilities and equity
Deposits	1,321,848		1,317,230
Deposits—intercompany	0		0
Securities loaned and sold under repurchase agreements	18,555		19,467
Securities loaned and sold under repurchase agreements—intercompany	(63,380)		(62,197)
Trading account liabilities	66,395		39,129
Trading account liabilities—intercompany	(2,765)		(1,277)
Short-term borrowings	21,682		14,548
Short-term borrowings—intercompany	(19,557)		(17,230)
Long-term debt	17,948		28,013
Long-term debt—intercompany	(86,144)		(76,335)
Advances from subsidiaries	(14,834)		(13,469)
Other liabilities	83,352		65,570
Other liabilities—intercompany	(18,062)		(11,774)
Stockholders’ equity	183,168		185,977
Total liabilities and equity	1,508,206		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	(222,196)		(223,303)
Other assets, net of allowance	0		0
Other assets—intercompany	0		0
Total assets	(222,196)		(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	(222,196)		(223,303)
Total liabilities and equity	$ (222,196)		$ (223,303)