LOANS AND LEASES - Schedule of Loans and Leases Delinquency Status (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 140,152	$ 139,037
Nonaccrual Loans	1,206	1,184
Total loans and leases	141,358	140,221	$ 135,370
Financing receivable, accrued interest reversed to nonaccrual status	7	14
Financing receivable, nonaccrual without allowance for credit loss	419	303
Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,029	751
30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	717	516
60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	178	126
90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	134	109
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	139,123	138,286
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	71,702	70,987
Nonaccrual Loans	838	812
Total loans and leases	72,540	71,799
Commercial | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	678	431
Commercial | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	417	245
Commercial | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	136	87
Commercial | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	125	99
Commercial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	71,024	70,556
Commercial | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5,520	5,100
Nonaccrual Loans	9	9
Total loans and leases	5,529	5,109
Commercial | Commercial construction | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	79	23
Commercial | Commercial construction | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	21	21
Commercial | Commercial construction | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	17	1
Commercial | Commercial construction | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	41	1
Commercial | Commercial construction | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5,441	5,077
Commercial | Owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,875	16,780
Nonaccrual Loans	76	62
Total loans and leases	16,951	16,842
Commercial | Owner occupied commercial mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	69	41
Commercial | Owner occupied commercial mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	59	30
Commercial | Owner occupied commercial mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	7	9
Commercial | Owner occupied commercial mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3	2
Commercial | Owner occupied commercial mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,806	16,739
Commercial | Non-owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,772	15,769
Nonaccrual Loans	367	425
Total loans and leases	16,139	16,194
Commercial | Non-owner occupied commercial mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	229	148
Commercial | Non-owner occupied commercial mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	104	43
Commercial | Non-owner occupied commercial mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	54	27
Commercial | Non-owner occupied commercial mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	71	78
Commercial | Non-owner occupied commercial mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,543	15,621
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	31,542	31,355
Nonaccrual Loans	357	285
Total loans and leases	31,899	31,640
Commercial | Commercial and industrial | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	244	173
Commercial | Commercial and industrial | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	185	118
Commercial | Commercial and industrial | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	50	39
Commercial | Commercial and industrial | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	9	16
Commercial | Commercial and industrial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	31,298	31,182
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,993	1,983
Nonaccrual Loans	29	31
Total loans and leases	2,022	2,014
Commercial | Leases | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	57	46
Commercial | Leases | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	48	33
Commercial | Leases | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	8	11
Commercial | Leases | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1	2
Commercial | Leases | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,936	1,937
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	27,951	28,047
Nonaccrual Loans	196	181
Total loans and leases	28,147	28,228
Consumer | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	267	256
Consumer | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	220	209
Consumer | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	38	37
Consumer | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	9	10
Consumer | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	27,684	27,791
Consumer | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22,899	23,004
Nonaccrual Loans	161	148
Total loans and leases	23,060	23,152
Consumer | Residential mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	222	206
Consumer | Residential mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	188	172
Total loans and leases	201	184
Consumer | Residential mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28	27
Total loans and leases	40	41
Consumer | Residential mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	6	7
Total loans and leases	107	99
Consumer | Residential mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22,677	22,798
Total loans and leases	22,712	22,828
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,609	2,543
Nonaccrual Loans	26	24
Total loans and leases	2,635	2,567
Consumer | Revolving mortgage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22	24
Consumer | Revolving mortgage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	17	20
Total loans and leases	20	22
Consumer | Revolving mortgage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	4
Total loans and leases	7	6
Consumer | Revolving mortgage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
Total loans and leases	11	11
Consumer | Revolving mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,587	2,519
Total loans and leases	2,597	2,528
Consumer | Consumer auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,479	1,515
Nonaccrual Loans	8	8
Total loans and leases	1,487	1,523
Consumer | Consumer auto | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	12	15
Consumer | Consumer auto | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	10	12
Total loans and leases	10	13
Consumer | Consumer auto | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	3
Total loans and leases	4	4
Consumer | Consumer auto | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
Total loans and leases	3	4
Consumer | Consumer auto | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,467	1,500
Total loans and leases	1,470	1,502
Consumer | Consumer other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	964	985
Nonaccrual Loans	1	1
Total loans and leases	965	986
Consumer | Consumer other | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	11	11
Consumer | Consumer other | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	5
Total loans and leases	6	5
Consumer | Consumer other | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3	3
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	3	3
Total loans and leases	3	3
Consumer | Consumer other | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	953	974
Total loans and leases	953	975
SVB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	40,499	40,003
Nonaccrual Loans	172	191
Total loans and leases	40,671	40,194
SVB | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	84	64
SVB | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	80	62
SVB | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4	2
SVB | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	40,415	39,939
SVB | Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28,572	27,904
Nonaccrual Loans	0	0
Total loans and leases	28,572	27,904
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	28,572	27,904
SVB | Investor dependent - early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	880	956
Nonaccrual Loans	28	41
Total loans and leases	908	997
SVB | Investor dependent - early stage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	6	9
SVB | Investor dependent - early stage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	8
SVB | Investor dependent - early stage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1	1
SVB | Investor dependent - early stage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Investor dependent - early stage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	874	947
SVB | Investor dependent - growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,008	2,150
Nonaccrual Loans	42	46
Total loans and leases	2,050	2,196
SVB | Investor dependent - growth stage | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5	2
SVB | Investor dependent - growth stage | 30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2	2
SVB | Investor dependent - growth stage | 60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3	0
SVB | Investor dependent - growth stage | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Investor dependent - growth stage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,003	2,148
SVB | Innovation C&I and cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	9,039	8,993
Nonaccrual Loans	102	104
Total loans and leases	9,141	9,097
SVB | Innovation C&I and cash flow dependent | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	73	53
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	73	52
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	1
SVB | Innovation C&I and cash flow dependent | 90 Days or Greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
SVB | Innovation C&I and cash flow dependent | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 8,966	$ 8,940