OTHER BORROWINGS (Textuals) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Securities pledged to secure retail repurchase agreements	$ 154,042,000
Funds Borrowed Against Current Borrowing Capacity	118,995,000	$ 95,860,000
Repurchase Agreements [Member] \| Retail repurchase agreements [Member]
Debt Instrument [Line Items]
Funds Borrowed Against Current Borrowing Capacity	$ 118,995,000	95,860,000
Repurchase Agreements [Member] \| Retail repurchase agreements [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Repurchase agreements, interest rate	0.10%
Repurchase Agreements [Member] \| Retail repurchase agreements [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Repurchase agreements, interest rate	0.55%
Federal Reserve Bank Advances [Member] \| Federal Reserve Bank of San Francisco [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 1,150,000,000
Funds Borrowed Against Current Borrowing Capacity	0	0
Subsidiary, Banner Bank [Member] \| Federal Funds Purchased [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	110,000,000
Line of credit, current	0	0
Balance outstanding	0
Subsidiary, Islanders Bank [Member] \| Federal Funds Purchased [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	5,000,000
Line of credit, current	$ 0	$ 0

Assets Sold under Agreements to Repurchase, Carrying Value Less Than 10 Percent of Total Assets, Interest Rate

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- Definition

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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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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- Definition

The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for repurchase agreements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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