LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Changes in the Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Allowance for loan losses
Balance at beginning of period	$ 696	$ 651	$ 684	$ 575
Provision for loan losses	1	44	34	136
Total	15	20	50	49
Recoveries	12	6	26	22
Net loan and lease charge-offs (recoveries)	3	14	24	27
Balance at end of period	694	681	694	681
Reserve for unfunded lending commitments
Balance at beginning of period	30	60	45	61
Provision for unfunded lending commitments	12	(3)	(3)	(4)
Balance at end of period	42	57	42	57
Total allowance for credit losses	736	738	736	738
Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				(3)
Adjusted balance
Allowance for loan losses
Balance at beginning of period				572
Commercial
Allowance for loan losses
Balance at beginning of period	302	323	302	300
Provision for loan losses	7	3	15	37
Total	12	12	30	35
Recoveries	9	5	19	17
Net loan and lease charge-offs (recoveries)	3	7	11	18
Balance at end of period	306	319	306	319
Reserve for unfunded lending commitments
Balance at beginning of period	16	20	19	16
Provision for unfunded lending commitments	4	1	1	5
Balance at end of period	20	21	20	21
Total allowance for credit losses	326	340	326	340
Commercial | Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				0
Commercial | Adjusted balance
Allowance for loan losses
Balance at beginning of period				300
Commercial real estate
Allowance for loan losses
Balance at beginning of period	300	181	241	156
Provision for loan losses	(13)	44	56	73
Total	0	3	11	3
Recoveries	2	0	3	0
Net loan and lease charge-offs (recoveries)	(2)	3	8	3
Balance at end of period	289	222	289	222
Reserve for unfunded lending commitments
Balance at beginning of period	7	29	17	33
Provision for unfunded lending commitments	5	(1)	(5)	(5)
Balance at end of period	12	28	12	28
Total allowance for credit losses	301	250	301	250
Commercial real estate | Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				(4)
Commercial real estate | Adjusted balance
Allowance for loan losses
Balance at beginning of period				152
Consumer
Allowance for loan losses
Balance at beginning of period	94	147	141	119
Provision for loan losses	7	(3)	(37)	26
Total	3	5	9	11
Recoveries	1	1	4	5
Net loan and lease charge-offs (recoveries)	2	4	5	6
Balance at end of period	99	140	99	140
Reserve for unfunded lending commitments
Balance at beginning of period	7	11	9	12
Provision for unfunded lending commitments	3	(3)	1	(4)
Balance at end of period	10	8	10	8
Total allowance for credit losses	$ 109	$ 148	$ 109	148
Consumer | Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				1
Consumer | Adjusted balance
Allowance for loan losses
Balance at beginning of period				$ 120