LOANS AND LEASES - Origination Year (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 2,011	$ 7,565
Fiscal year before current fiscal year	6,812	4,429
Two years before current fiscal year	4,171	2,837
Three years before current fiscal year	2,642	2,281
Four years before current fiscal year	2,103	1,800
Prior	5,320	3,917
Revolving Loans Amortized Cost Basis	2,473	2,630
Total Loans and Leases	25,532	25,459
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	328	1,892
Fiscal year before current fiscal year	1,896	1,916
Two years before current fiscal year	1,939	1,244
Three years before current fiscal year	1,214	1,166
Four years before current fiscal year	1,105	1,074
Prior	3,162	2,266
Revolving Loans Amortized Cost Basis	155	173
Total Loans and Leases	9,799	9,731
Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	323	1,879
Fiscal year before current fiscal year	1,876	1,854
Two years before current fiscal year	1,874	1,135
Three years before current fiscal year	1,080	927
Four years before current fiscal year	881	888
Prior	2,680	1,911
Revolving Loans Amortized Cost Basis	145	163
Total Loans and Leases	8,859	8,757
Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5	9
Fiscal year before current fiscal year	12	30
Two years before current fiscal year	32	80
Three years before current fiscal year	93	158
Four years before current fiscal year	151	70
Prior	191	163
Revolving Loans Amortized Cost Basis	5	4
Total Loans and Leases	489	514
Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	4
Fiscal year before current fiscal year	8	32
Two years before current fiscal year	33	29
Three years before current fiscal year	41	81
Four years before current fiscal year	73	116
Prior	291	192
Revolving Loans Amortized Cost Basis	5	6
Total Loans and Leases	451	460
Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,118	3,324
Fiscal year before current fiscal year	2,682	1,056
Two years before current fiscal year	969	668
Three years before current fiscal year	627	376
Four years before current fiscal year	353	136
Prior	465	383
Revolving Loans Amortized Cost Basis	1,187	1,271
Total Loans and Leases	7,401	7,214
Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,116	3,286
Fiscal year before current fiscal year	2,642	1,007
Two years before current fiscal year	921	590
Three years before current fiscal year	561	304
Four years before current fiscal year	280	120
Prior	354	311
Revolving Loans Amortized Cost Basis	1,030	1,095
Total Loans and Leases	6,904	6,713
Commercial and Industrial [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	30
Fiscal year before current fiscal year	32	23
Two years before current fiscal year	20	13
Three years before current fiscal year	9	28
Four years before current fiscal year	28	10
Prior	67	35
Revolving Loans Amortized Cost Basis	53	79
Total Loans and Leases	209	218
Commercial and Industrial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2	8
Fiscal year before current fiscal year	8	26
Two years before current fiscal year	28	65
Three years before current fiscal year	57	44
Four years before current fiscal year	45	6
Prior	44	37
Revolving Loans Amortized Cost Basis	104	97
Total Loans and Leases	288	283
Commercial Leases [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	34	186
Fiscal year before current fiscal year	166	137
Two years before current fiscal year	128	89
Three years before current fiscal year	78	61
Four years before current fiscal year	56	7
Prior	9	5
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	471	485
Commercial Leases [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	34	178
Fiscal year before current fiscal year	158	134
Two years before current fiscal year	124	83
Three years before current fiscal year	73	56
Four years before current fiscal year	52	5
Prior	6	3
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	447	459
Commercial Leases [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
Fiscal year before current fiscal year	0	1
Two years before current fiscal year	1	4
Three years before current fiscal year	3	4
Four years before current fiscal year	3	1
Prior	3	2
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	10	13
Commercial Leases [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	7
Fiscal year before current fiscal year	8	2
Two years before current fiscal year	3	2
Three years before current fiscal year	2	1
Four years before current fiscal year	1	1
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	14	13
Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	4	5
Revolving Loans Amortized Cost Basis	15	35
Total Loans and Leases	25	40
Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	4	4
Revolving Loans Amortized Cost Basis	15	35
Total Loans and Leases	25	39
Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	1
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	0	1
Total Commercial Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,486	5,402
Fiscal year before current fiscal year	4,744	3,109
Two years before current fiscal year	3,036	2,001
Three years before current fiscal year	1,919	1,603
Four years before current fiscal year	1,514	1,217
Prior	3,640	2,659
Revolving Loans Amortized Cost Basis	1,357	1,479
Total Loans and Leases	17,696	17,470
Direct Installment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	154	706
Fiscal year before current fiscal year	676	338
Two years before current fiscal year	307	202
Three years before current fiscal year	183	144
Four years before current fiscal year	131	173
Prior	574	456
Revolving Loans Amortized Cost Basis	0	1
Total Loans and Leases	2,025	2,020
Direct Installment [Member] | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	154	706
Fiscal year before current fiscal year	676	337
Two years before current fiscal year	306	200
Three years before current fiscal year	182	143
Four years before current fiscal year	130	171
Prior	560	442
Revolving Loans Amortized Cost Basis	0	1
Total Loans and Leases	2,008	2,000
Direct Installment [Member] | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	1
Two years before current fiscal year	1	2
Three years before current fiscal year	1	1
Four years before current fiscal year	1	2
Prior	14	14
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	17	20
Residential Mortgages [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	248	1,080
Fiscal year before current fiscal year	1,034	712
Two years before current fiscal year	588	290
Three years before current fiscal year	242	382
Four years before current fiscal year	331	336
Prior	885	632
Revolving Loans Amortized Cost Basis	1	1
Total Loans and Leases	3,329	3,433
Residential Mortgages [Member] | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	248	1,079
Fiscal year before current fiscal year	1,033	707
Two years before current fiscal year	586	283
Three years before current fiscal year	239	378
Four years before current fiscal year	327	330
Prior	856	603
Revolving Loans Amortized Cost Basis	1	1
Total Loans and Leases	3,290	3,381
Residential Mortgages [Member] | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
Fiscal year before current fiscal year	1	5
Two years before current fiscal year	2	7
Three years before current fiscal year	3	4
Four years before current fiscal year	4	6
Prior	29	29
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	39	52
Indirect Installment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	122	373
Fiscal year before current fiscal year	354	263
Two years before current fiscal year	235	336
Three years before current fiscal year	290	149
Four years before current fiscal year	124	69
Prior	76	28
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	1,201	1,218
Indirect Installment [Member] | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	122	372
Fiscal year before current fiscal year	353	260
Two years before current fiscal year	233	332
Three years before current fiscal year	289	147
Four years before current fiscal year	123	67
Prior	75	27
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	1,195	1,205
Indirect Installment [Member] | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
Fiscal year before current fiscal year	1	3
Two years before current fiscal year	2	4
Three years before current fiscal year	1	2
Four years before current fiscal year	1	2
Prior	1	1
Revolving Loans Amortized Cost Basis	0	0
Total Loans and Leases	6	13
Consumer Lines of Credit [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1	4
Fiscal year before current fiscal year	4	7
Two years before current fiscal year	5	8
Three years before current fiscal year	8	3
Four years before current fiscal year	3	5
Prior	145	142
Revolving Loans Amortized Cost Basis	1,115	1,149
Total Loans and Leases	1,281	1,318
Consumer Lines of Credit [Member] | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1	4
Fiscal year before current fiscal year	4	7
Two years before current fiscal year	5	8
Three years before current fiscal year	8	3
Four years before current fiscal year	3	5
Prior	132	127
Revolving Loans Amortized Cost Basis	1,114	1,146
Total Loans and Leases	1,267	1,300
Consumer Lines of Credit [Member] | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	13	15
Revolving Loans Amortized Cost Basis	1	3
Total Loans and Leases	14	18
Consumer Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	525	2,163
Fiscal year before current fiscal year	2,068	1,320
Two years before current fiscal year	1,135	836
Three years before current fiscal year	723	678
Four years before current fiscal year	589	583
Prior	1,680	1,258
Revolving Loans Amortized Cost Basis	1,116	1,151
Total Loans and Leases	$ 7,836	$ 7,989