LOANS AND LEASES - Schedule of Nonaccrual Status (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	$ 1,244	$ 969
Loans > 90 Days and Accruing	131	123
Financing receivable, accrued interest reversed to nonaccrual status	11	10
Financing receivable, nonaccrual without allowance for credit loss	303	138
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	868	698
Loans > 90 Days and Accruing	121	114
Commercial | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	4	2
Loans > 90 Days and Accruing	3	1
Commercial | Owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	76	60
Loans > 90 Days and Accruing	7	8
Commercial | Non-owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	469	411
Loans > 90 Days and Accruing	86	39
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	288	194
Loans > 90 Days and Accruing	24	59
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	31	31
Loans > 90 Days and Accruing	1	7
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	169	154
Loans > 90 Days and Accruing	10	7
Consumer | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	138	127
Loans > 90 Days and Accruing	7	4
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	22	21
Loans > 90 Days and Accruing	0	0
Consumer | Consumer auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	7	5
Loans > 90 Days and Accruing	0	0
Consumer | Consumer other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	2	1
Loans > 90 Days and Accruing	3	3
SVB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	207	117
Loans > 90 Days and Accruing	0	2
SVB | Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	0	0
Loans > 90 Days and Accruing	0	0
SVB | Investor dependent - early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	56	37
Loans > 90 Days and Accruing	0	2
SVB | Investor dependent - growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	35	37
Loans > 90 Days and Accruing	0	0
SVB | Innovation C&I and cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual Loans	116	43
Loans > 90 Days and Accruing	$ 0	$ 0