LOANS AND LEASES - Schedule of Loans and Leases Delinquency Status (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 139,341	$ 133,302	$ 133,015
Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,411	1,550
30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	518	606
60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	203	329
90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	690	615
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	137,930	131,752
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	69,030	66,232
Commercial | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,008	1,135
Commercial | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	346	396
Commercial | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	93	270
Commercial | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	569	469
Commercial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	68,022	65,097
Commercial | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4,484	3,918
Commercial | Commercial construction | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	74	53
Commercial | Commercial construction | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	74	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	4,410	3,865
Commercial | Owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,233	15,471
Commercial | Owner occupied commercial mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	95	78
Commercial | Owner occupied commercial mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	52	21
Commercial | Owner occupied commercial mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	14	10
Commercial | Owner occupied commercial mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	29	47
Commercial | Owner occupied commercial mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,138	15,393
Commercial | Non-owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,580	14,995
Commercial | Non-owner occupied commercial mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	480	571
Commercial | Non-owner occupied commercial mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	66	100
Commercial | Non-owner occupied commercial mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	188
Commercial | Non-owner occupied commercial mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	412	283
Commercial | Non-owner occupied commercial mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,100	14,424
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	30,684	29,794
Commercial | Commercial and industrial | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	292	342
Commercial | Commercial and industrial | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	111	177
Commercial | Commercial and industrial | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	64	49
Commercial | Commercial and industrial | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	117	116
Commercial | Commercial and industrial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	30,392	29,452
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,049	2,054
Commercial | Leases | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	67	91
Commercial | Leases | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	43	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	11	21
Commercial | Leases | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,982	1,963
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28,343	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	170	168
Consumer | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	61	42
Consumer | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	96	90
Consumer | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28,016	27,259
Consumer | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	23,101	22,776
Consumer | Residential mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	271	242
Consumer | Residential mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	142	136
Consumer | Residential mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	50	33
Consumer | Residential mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	79	73
Consumer | Residential mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22,830	22,534
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,351	2,165
Consumer | Revolving mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	31	29
Consumer | Revolving mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15	15
Consumer | Revolving mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	3
Consumer | Revolving mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	11	11
Consumer | Revolving mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,320	2,136
Consumer | Consumer auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,503	1,442
Consumer | Consumer auto | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	14	14
Consumer | Consumer auto | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	9	9
Consumer | Consumer auto | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3	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	1,489	1,428
Consumer | Consumer other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,388	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	4	8
Consumer | Consumer other | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3	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	1,377	1,161
SVB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	41,968	39,511
SVB | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	76	115
SVB | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	42
SVB | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	49	17
SVB | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	25	56
SVB | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	41,892	39,396
SVB | Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28,915	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	28,915	25,553
SVB | Investor dependent - early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,179	1,403
SVB | Investor dependent - early stage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	11	31
SVB | Investor dependent - early stage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	10
SVB | Investor dependent - early stage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	12
SVB | Investor dependent - early stage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	7	9
SVB | Investor dependent - early stage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,168	1,372
SVB | Investor dependent - growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,627	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	0	5
SVB | Investor dependent - growth stage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	6	2
SVB | Investor dependent - growth stage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	7
SVB | Investor dependent - growth stage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,616	2,883
SVB | Innovation C&I and cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	9,247	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	54	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	0	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	41	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	13	40
SVB | Innovation C&I and cash flow dependent | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 9,193	$ 9,588