CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	$ 2,086	$ 2,017	$ 2,098	$ 1,983
Charge-offs	(223)	(189)	(454)	(360)
Recoveries	39	37	89	75
Net charge-offs	(184)	(152)	(365)	(285)
Provision expense (benefit) for loans and leases	223	179	392	346
Allowance for loan and lease losses, end of period	2,125	2,044	2,125	2,044
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	222	258	220	257
Provision expense (benefit) for unfunded lending commitments	(41)	(3)	(39)	(2)
Allowance for unfunded lending commitments, end of period	181	255	181	255
Total allowance for credit losses, end of period	2,306	2,299	2,306	2,299
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	1,234	1,111	1,250	1,060
Charge-offs	(100)	(79)	(202)	(138)
Recoveries	4	3	21	10
Net charge-offs	(96)	(76)	(181)	(128)
Provision expense (benefit) for loans and leases	144	122	213	225
Allowance for loan and lease losses, end of period	1,282	1,157	1,282	1,157
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	191	215	175	207
Provision expense (benefit) for unfunded lending commitments	(44)	(2)	(28)	6
Allowance for unfunded lending commitments, end of period	147	213	147	213
Total allowance for credit losses, end of period	1,429	1,370	1,429	1,370
Retail
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	852	906	848	923
Charge-offs	(123)	(110)	(252)	(222)
Recoveries	35	34	68	65
Net charge-offs	(88)	(76)	(184)	(157)
Provision expense (benefit) for loans and leases	79	57	179	121
Allowance for loan and lease losses, end of period	843	887	843	887
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	31	43	45	50
Provision expense (benefit) for unfunded lending commitments	3	(1)	(11)	(8)
Allowance for unfunded lending commitments, end of period	34	42	34	42
Total allowance for credit losses, end of period	$ 877	$ 929	$ 877	$ 929