LOANS RECEIVABLE AND THE ALLOWANCE FOR CREDIT LOSSES (Loans by Type) (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	100.00%	100.00%
Unearned loan fees in excess of unamortized costs	$ 16,500	$ 15,500
Discount on acquired loans, net	2,700	3,500
Financing Receivable, Accrued Interest, before Allowance for Credit Loss	53,300	47,700
Financing Receivable, Loans Held as Collateral, FHLB and Other Borrowings	8,200,000	7,900,000
Financing Receivable, before Allowance for Credit Loss	11,702,538	11,354,656
Financing Receivable, after Allowance for Credit Loss	$ 11,542,831	$ 11,199,135
Commerical real estate - owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	10.00%	9.00%
Financing Receivable, before Allowance for Credit Loss	$ 1,134,559	$ 1,027,426
Commercial real estate - investment properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	14.00%	14.00%
Financing Receivable, before Allowance for Credit Loss	$ 1,652,141	$ 1,623,672
Small balance CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	10.00%	11.00%
Financing Receivable, before Allowance for Credit Loss	$ 1,210,357	$ 1,213,792
Multifamily Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	7.00%	8.00%
Financing Receivable, before Allowance for Credit Loss	$ 860,650	$ 894,425
Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	1.00%	1.00%
Financing Receivable, before Allowance for Credit Loss	$ 144,125	$ 122,362
Multifamily construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	5.00%	5.00%
Financing Receivable, before Allowance for Credit Loss	$ 586,104	$ 513,706
One- to four- family construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	5.00%	5.00%
Financing Receivable, before Allowance for Credit Loss	$ 578,128	$ 514,220
Land and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	4.00%	3.00%
Financing Receivable, before Allowance for Credit Loss	$ 427,348	$ 369,663
Commercial Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	11.00%	11.00%
Financing Receivable, before Allowance for Credit Loss	$ 1,254,460	$ 1,318,333
Small business scored
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	10.00%	10.00%
Financing Receivable, before Allowance for Credit Loss	$ 1,176,889	$ 1,104,117
Agricultural business, including secured by farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	3.00%	3.00%
Financing Receivable, before Allowance for Credit Loss	$ 354,884	$ 340,280
One- to four-family residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	14.00%	14.00%
Financing Receivable, before Allowance for Credit Loss	$ 1,582,605	$ 1,591,260
Consumer—home equity revolving lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	5.00%	5.00%
Financing Receivable, before Allowance for Credit Loss	$ 649,188	$ 625,680
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total loans	1.00%	1.00%
Financing Receivable, before Allowance for Credit Loss	$ 91,100	$ 95,720

BANNER CORP 10-Q