LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Past Due Loans (Accruing and Nonaccruing)) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 58,884	$ 57,779
90+ days past due	7	3
Nonaccrual loans that are current	363	222
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,785	30,588
90+ days past due	6	2
Nonaccrual loans that are current	215	104
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,483	13,371
90+ days past due	0	0
Nonaccrual loans that are current	69	61
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14,616	13,820
90+ days past due	1	1
Nonaccrual loans that are current	79	57
Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,757	16,684
90+ days past due	6	1
Nonaccrual loans that are current	173	82
Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	377	383
90+ days past due	0	0
Nonaccrual loans that are current	2	2
Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,381	9,219
90+ days past due	0	1
Nonaccrual loans that are current	29	20
Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,270	4,302
90+ days past due	0	0
Nonaccrual loans that are current	11
Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,833	2,669
90+ days past due	0	0
Nonaccrual loans that are current	2	22
Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,650	10,702
90+ days past due	0	0
Nonaccrual loans that are current	67	39
Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,543	3,356
90+ days past due	0	0
Nonaccrual loans that are current	30	17
1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,489	8,415
90+ days past due	0	0
Nonaccrual loans that are current	47	40
Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	997	1,442
90+ days past due	0	0
Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	461	474
90+ days past due	1	1
Nonaccrual loans that are current	1
Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	126	133
90+ days past due	0	0
Nonaccrual loans that are current	1
Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	58,662	57,576
Current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,669	30,519
Current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,444	13,306
Current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14,549	13,751
Current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,691	16,631
Current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	376	381
Current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,359	9,206
Current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,243	4,301
Current | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,828	2,645
Current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,616	10,661
Current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,521	3,334
Current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,450	8,375
Current | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	996	1,442
Current | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	457	468
Current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	125	132
Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	222	203
Total past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	116	69
Total past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	39	65
Total past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	67	69
Total past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	66	53
Total past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	2
Total past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	22	13
Total past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	27	1
Total past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	5	24
Total past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	34	41
Total past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	22	22
Total past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	39	40
Total past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	0
Total past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4	6
Total past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	1
30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	111	108
30-89 days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	78	52
30-89 days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6	16
30-89 days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	27	40
30-89 days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	35	38
30-89 days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	2
30-89 days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	15	11
30-89 days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	27	1
30-89 days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	2
30-89 days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	14
30-89 days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12	17
30-89 days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10	17
30-89 days past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	0
30-89 days past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	5
30-89 days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	1
90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	111	95
90+ days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	38	17
90+ days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	33	49
90+ days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	40	29
90+ days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	31	15
90+ days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	7	2
90+ days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	22
90+ days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	31	27
90+ days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10	5
90+ days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	29	23
90+ days past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	1
90+ days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
Nonaccrual loans that are current
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	237	108
Nonaccrual loans that are current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	169	83
Nonaccrual loans that are current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	37	3
Nonaccrual loans that are current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	31	22
Nonaccrual loans that are current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	140	65
Nonaccrual loans that are current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	1	0
Nonaccrual loans that are current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	17	18
Nonaccrual loans that are current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	11	0
Nonaccrual loans that are current | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	37	3
Nonaccrual loans that are current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	15	9
Nonaccrual loans that are current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	15	13
Nonaccrual loans that are current | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	$ 1	$ 0