CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	$ 2,061	$ 2,098
Charge-offs	(234)	(231)
Recoveries	34	50
Net charge-offs	(200)	(181)
Provision expense (benefit) for loans and leases	153	169
Allowance for loan and lease losses, end of period	2,014	2,086
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	198	220
Provision expense (benefit) for unfunded lending commitments	0	2
Allowance for unfunded lending commitments, end of period	198	222
Total allowance for credit losses, end of period	2,212	2,308
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	1,140	1,250
Charge-offs	(85)	(102)
Recoveries	4	17
Net charge-offs	(81)	(85)
Provision expense (benefit) for loans and leases	89	69
Allowance for loan and lease losses, end of period	1,148	1,234
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	155	175
Provision expense (benefit) for unfunded lending commitments	9	16
Allowance for unfunded lending commitments, end of period	164	191
Total allowance for credit losses, end of period	1,312	1,425
Retail
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses, beginning of period	921	848
Charge-offs	(149)	(129)
Recoveries	30	33
Net charge-offs	(119)	(96)
Provision expense (benefit) for loans and leases	64	100
Allowance for loan and lease losses, end of period	866	852
Unfunded lending commitments [Roll Forward]
Allowance for unfunded lending commitments, beginning of period	43	45
Provision expense (benefit) for unfunded lending commitments	(9)	(14)
Allowance for unfunded lending commitments, end of period	34	31
Total allowance for credit losses, end of period	$ 900	$ 883