SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revision of cash flows (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other, net	[1]	$ (17,922)	$ (15,446)	$ 1,246
Impact to cash from (used in) operating activities	[1]	25,069	47,090	(23,488)
AFS purchases	[1],[2]	(218,747)	(205,980)	(306,801)
AFS maturities	[2]	140,934	120,936	110,941
Impact to cash from (used in) investing activities	[1]	$ (79,455)	(110,746)	(92,445)
Cash flows related to negotiable certificates of deposit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other, net			(17,402)	1,216
AFS purchases			(205,980)	(306,801)
AFS maturities			120,936	110,941
As reported | Cash flows related to negotiable certificates of deposit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other, net			(1,287)	4,113
AFS purchases			(222,095)	(307,771)
AFS maturities			120,936	109,014
Revision
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Impact to cash from (used in) operating activities			2,000	30
Impact to cash from (used in) investing activities			(2,000)	(30)
Revision | Cash flows related to negotiable certificates of deposit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other, net			(16,115)	(2,897)
Impact to cash from (used in) operating activities			(16,115)	(2,897)
AFS purchases			16,115	970
AFS maturities			0	1,927
Impact to cash from (used in) investing activities			$ 16,115	$ 2,897

[1] See “Statement of Cash Flows” in Note 1.

[2] Citi has revised the Consolidated Statement of Cash Flows to present purchases of investments, sales of investments and proceeds from maturities of investments separately between AFS debt securities and HTM debt securities. Citi had no sales of HTM debt securities during the periods presented.