ALLOWANCE FOR CREDIT LOSSES - Allowance Roll-forward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Financing Receivable, Allowance for Credit Loss [Roll Forward]
ALLL balance, beginning of period	$ 2,537	$ 2,244
Loan and lease charge-offs	(173)
Loan and lease charge-offs	(173)	(133)
Recoveries of loans and leases previously charged-off	62	47
Provision for loan and lease losses	250	105
Allowance on PCD loans and leases at acquisition	322
Allowance on purchased seasoned loans and leases at acquisition	245
ALLL balance, end of period	3,243	2,263
AULC balance, beginning of period	206	202
Provision (benefit) for unfunded lending commitments	(92)	13
Acquired unfunded lending commitments	11
AULC balance, end of period	125	215
ACL balance, end of period	3,368	2,478
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
ALLL balance, beginning of period	1,731	1,484
Loan and lease charge-offs	(98)
Loan and lease charge-offs		(74)
Recoveries of loans and leases previously charged-off	42	30
Provision for loan and lease losses	192	80
Allowance on PCD loans and leases at acquisition	268
Allowance on purchased seasoned loans and leases at acquisition	170
ALLL balance, end of period	2,305	1,520
AULC balance, beginning of period	145	144
Provision (benefit) for unfunded lending commitments	(50)	14
Acquired unfunded lending commitments	3
AULC balance, end of period	98	158
ACL balance, end of period	2,403	1,678
Commercial | Cadence
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Loan and lease charge-offs	(23)
ALLL balance, end of period	438
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
ALLL balance, beginning of period	806	760
Loan and lease charge-offs	(75)
Loan and lease charge-offs		(59)
Recoveries of loans and leases previously charged-off	20	17
Provision for loan and lease losses	58	25
Allowance on PCD loans and leases at acquisition	54
Allowance on purchased seasoned loans and leases at acquisition	75
ALLL balance, end of period	938	743
AULC balance, beginning of period	61	58
Provision (benefit) for unfunded lending commitments	(42)	(1)
Acquired unfunded lending commitments	8
AULC balance, end of period	27	57
ACL balance, end of period	965	$ 800
Consumer | Cadence
Financing Receivable, Allowance for Credit Loss [Roll Forward]
ALLL balance, end of period	$ 129