LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of PCD AND PSL Loans Acquired (Details) $ in Millions	Aug. 20, 2026 USD ($)
SHUSA
Loans Receivable [Line Items]
UPB (1)	$ 58,034
Noncredit discount (premium)	1,447
Amortized cost basis, excluding allowance	56,587
Allowance for credit losses at acquisition	856
Amortized cost basis, net of allowance	55,731
Webster
Loans Receivable [Line Items]
Allowance for credit losses at acquisition	229
PCD \| SHUSA
Loans Receivable [Line Items]
UPB (1)	2,371
Noncredit discount (premium)	112
Amortized cost basis, excluding allowance	2,259
Allowance for credit losses at acquisition	323
Amortized cost basis, net of allowance	1,936
PSL \| SHUSA
Loans Receivable [Line Items]
UPB (1)	55,663
Noncredit discount (premium)	1,335
Amortized cost basis, excluding allowance	54,328
Allowance for credit losses at acquisition	533
Amortized cost basis, net of allowance	$ 53,795

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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