LOANS AND LEASES - Schedule of Loans by Class (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 141,358	$ 140,221	$ 135,370
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	72,540	71,799
Commercial | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	5,529	5,109
Commercial | Owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,951	16,842
Commercial | Non-owner occupied commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	16,139	16,194
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	31,899	31,640
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,022	2,014
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	28,147	28,228
Consumer | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	23,060	23,152
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,635	2,567
Consumer | Consumer auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,487	1,523
Consumer | Consumer other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	965	986
SVB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	40,671	40,194
SVB | Global fund banking
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	908	997
SVB | Investor dependent - growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	2,050	2,196
SVB | Innovation C&I and cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 9,141	$ 9,097