SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Assets and Liabilities of VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Cash	$ 26,502		$ 27,515	$ 28,906
Trading account assets	358,260		331,945
Investments	508,016		512,822
Loans, net of unearned income	645,960		667,767
Allowance for credit losses on loans (ACLL)	(16,309)	$ (15,952)	(16,455)	(17,715)	$ (19,238)	$ (24,956)
Total loans, net	629,651		651,312
Other assets, at fair value	132,809		125,879
Total assets	2,381,064		2,291,413
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	47,368		27,973
Long-term debt	253,068		254,374
Other liabilities	87,276		74,920
Total liabilities	2,181,947		2,088,741
Consumer
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	357,583		376,534
Allowance for credit losses on loans (ACLL)	(13,361)	(12,983)	(14,040)	(15,105)	(16,566)	(20,180)
Corporate
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	288,377		291,233
Allowance for credit losses on loans (ACLL)	(2,948)	$ (2,969)	(2,415)	$ (2,610)	$ (2,672)	$ (4,776)
Consolidated VIEs
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Cash	63		260
Trading account assets	8,274		10,038
Investments	616		844
Loans, net of unearned income	50,148		48,989
Allowance for credit losses on loans (ACLL)	(2,446)		(2,668)
Total loans, net	47,702		46,321
Other assets, at fair value	71		1,174
Total assets	56,726		58,637
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	10,073		8,376
Long-term debt	10,438		12,579
Other liabilities	266		694
Total liabilities	20,777		21,649
Consolidated VIEs | Consumer
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	34,333		34,677
Consolidated VIEs | Corporate
Assets of consolidated VIEs to be used to settle obligations of consolidated VIEs
Loans, net of unearned income	$ 15,815		$ 14,312