CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	$ 2,008	$ 2,125	$ 2,061	$ 2,098
Charge-offs	(195)	(231)	(630)	(685)
Recoveries	33	39	101	128
Net charge-offs	(162)	(192)	(529)	(557)
Provision expense (benefit) for loans and leases	126	146	440	538
Allowance for loan and lease losses, end of period	1,972	2,079	1,972	2,079
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	201	181	198	220
Provision expense (benefit) for unfunded lending commitments	28	26	31	(13)
Allowance for unfunded lending commitments, end of period	229	207	229	207
Total allowance for credit losses, end of period	2,201	2,286	2,201	2,286
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	1,106	1,282	1,140	1,250
Charge-offs	(91)	(106)	(269)	(308)
Recoveries	6	8	11	29
Net charge-offs	(85)	(98)	(258)	(279)
Provision expense (benefit) for loans and leases	62	3	201	216
Allowance for loan and lease losses, end of period	1,083	1,187	1,083	1,187
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	163	147	155	175
Provision expense (benefit) for unfunded lending commitments	19	17	27	(11)
Allowance for unfunded lending commitments, end of period	182	164	182	164
Total allowance for credit losses, end of period	1,265	1,351	1,265	1,351
Retail
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	902	843	921	848
Charge-offs	(104)	(125)	(361)	(377)
Recoveries	27	31	90	99
Net charge-offs	(77)	(94)	(271)	(278)
Provision expense (benefit) for loans and leases	64	143	239	322
Allowance for loan and lease losses, end of period	889	892	889	892
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	38	34	43	45
Provision expense (benefit) for unfunded lending commitments	9	9	4	(2)
Allowance for unfunded lending commitments, end of period	47	43	47	43
Total allowance for credit losses, end of period	$ 936	$ 935	$ 936	$ 935