COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Commissions and Fees Revenue (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022
Commissions and fees
Total commissions and fees	$ 2,724	$ 2,366
Investment Banking
Commissions and fees
Total commissions and fees	873	726
Brokerage Commissions
Commissions and fees
Total commissions and fees	619	637
Revenue recognized	108		$ 116
Interchange fees
Commissions and fees
Total commissions and fees	2,911	2,849
Card-related loan fees
Commissions and fees
Total commissions and fees	130	118
Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,917)	(2,928)
Deposit-related fees
Commissions and fees
Total commissions and fees	340	299
Transactional service fees
Commissions and fees
Total commissions and fees	340	319
Corporate finance
Commissions and fees
Total commissions and fees	199	102
Insurance distribution revenue
Commissions and fees
Total commissions and fees	84	92
Insurance premiums
Commissions and fees
Total commissions and fees	25	22
Loan servicing
Commissions and fees
Total commissions and fees	14	28
Other
Commissions and fees
Total commissions and fees	106	102
Commissions and fees
Commissions and fees
Commissions and fees	$ (2,538)	$ (2,656)