FAIR VALUE ELECTIONS - Changes in Fair Value Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Securities borrowed and purchased under agreements to resell
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	$ (6)	$ (95)	$ (59)	$ (10)
Trading account assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(5)	18	2	79
Certain corporate loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	160	635	1,378	326
Certain consumer loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(2)	(4)	(10)	1
Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	158	631	1,368	327
MSRs
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	5	22	17	19
Certain mortgage loans HFS
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	4	(18)	5	(10)
Total other assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	9	4	22	9
Total assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	156	558	1,333	405
Interest-bearing deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(21)	82	(63)	(52)
Securities loaned and sold under agreements to repurchase
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(10)	49	26	(19)
Trading account liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(153)	77	(224)	152
Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(79)	230	(381)	88
Long-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	(194)	(2,147)	(2,122)	(6,496)
Total liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions.
Gain (loss) from changes in fair value	$ (457)	$ (1,709)	$ (2,764)	$ (6,327)