LOANS AND LEASES - Schedule of Loans by Class (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
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	69,030	66,232
Commercial | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4,484	3,918
Commercial | Owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,233	15,471
Commercial | Non-owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	15,580	14,995
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	30,684	29,794
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,049	2,054
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28,343	27,559
Consumer | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	23,101	22,776
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,351	2,165
Consumer | Consumer auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,503	1,442
Consumer | Consumer other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,388	1,176
SVB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	41,968	39,511
SVB | Global fund banking
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 - growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,627	2,897
SVB | Innovation C&I and cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 9,247	$ 9,658