LOANS AND LEASES - Schedule of Loans and Leases Delinquency Status (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 135,370	$ 133,302	$ 138,288
Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,522	1,550
30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	661	606
60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	179	329
90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	682	615
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	133,848	131,752
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	67,601	66,232
Commercial | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,116	1,135
Commercial | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	438	396
Commercial | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	132	270
Commercial | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	546	469
Commercial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	66,485	65,097
Commercial | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4,062	3,918
Commercial | Commercial construction | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	40	53
Commercial | Commercial construction | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	40	43
Commercial | Commercial construction | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	8
Commercial | Commercial construction | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	2
Commercial | Commercial construction | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4,022	3,865
Commercial | Owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,979	15,471
Commercial | Owner occupied commercial mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	96	78
Commercial | Owner occupied commercial mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	37	21
Commercial | Owner occupied commercial mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	13	10
Commercial | Owner occupied commercial mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	46	47
Commercial | Owner occupied commercial mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,883	15,393
Commercial | Non-owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,329	14,995
Commercial | Non-owner occupied commercial mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	521	571
Commercial | Non-owner occupied commercial mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	118	100
Commercial | Non-owner occupied commercial mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	34	188
Commercial | Non-owner occupied commercial mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	369	283
Commercial | Non-owner occupied commercial mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	14,808	14,424
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	30,164	29,794
Commercial | Commercial and industrial | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	382	342
Commercial | Commercial and industrial | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	191	177
Commercial | Commercial and industrial | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	72	49
Commercial | Commercial and industrial | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	119	116
Commercial | Commercial and industrial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	29,782	29,452
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,067	2,054
Commercial | Leases | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	77	91
Commercial | Leases | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	52	55
Commercial | Leases | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	13	15
Commercial | Leases | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	12	21
Commercial | Leases | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,990	1,963
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	27,923	27,559
Consumer | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	327	300
Consumer | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	184	168
Consumer | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	45	42
Consumer | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	98	90
Consumer | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	27,596	27,259
Consumer | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22,901	22,776
Consumer | Residential mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	277	242
Consumer | Residential mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	157	136
Consumer | Residential mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	38	33
Consumer | Residential mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	82	73
Consumer | Residential mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22,624	22,534
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,240	2,165
Consumer | Revolving mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	27	29
Consumer | Revolving mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	14	15
Consumer | Revolving mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3	3
Consumer | Revolving mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	10	11
Consumer | Revolving mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,213	2,136
Consumer | Consumer auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,476	1,442
Consumer | Consumer auto | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	12	14
Consumer | Consumer auto | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	8	9
Consumer | Consumer auto | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	3
Consumer | Consumer auto | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	2
Consumer | Consumer auto | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,464	1,428
Consumer | Consumer other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,306	1,176
Consumer | Consumer other | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	11	15
Consumer | Consumer other | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	8
Consumer | Consumer other | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	3
Consumer | Consumer other | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4	4
Consumer | Consumer other | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,295	1,161
SVB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	39,846	39,511
SVB | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	79	115
SVB | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	39	42
SVB | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	17
SVB | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	38	56
SVB | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	39,767	39,396
SVB | Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	26,518	25,553
SVB | Global fund banking | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Global fund banking | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Global fund banking | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Global fund banking | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Global fund banking | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	26,518	25,553
SVB | Investor dependent - early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,293	1,403
SVB | Investor dependent - early stage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	39	31
SVB | Investor dependent - early stage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	30	10
SVB | Investor dependent - early stage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1	12
SVB | Investor dependent - early stage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	8	9
SVB | Investor dependent - early stage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,254	1,372
SVB | Investor dependent - growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,696	2,897
SVB | Investor dependent - growth stage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	11	14
SVB | Investor dependent - growth stage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	8	5
SVB | Investor dependent - growth stage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1	2
SVB | Investor dependent - growth stage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	7
SVB | Investor dependent - growth stage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,685	2,883
SVB | Innovation C&I and cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	9,339	9,658
SVB | Innovation C&I and cash flow dependent | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	29	70
SVB | Innovation C&I and cash flow dependent | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1	27
SVB | Innovation C&I and cash flow dependent | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	3
SVB | Innovation C&I and cash flow dependent | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28	40
SVB | Innovation C&I and cash flow dependent | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 9,310	$ 9,588