ADVANCES FROM FEDERAL HOME LOAN BANK OF DES MOINES (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Advances from Federal Home Loan Banks [Abstract]
Federal Home Loan Bank, advances, collateral pledged	$ 0
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Maturing in one year or less	$ 540,000,000	$ 0
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate	2.64%	0.00%
Maturing after one year through three years	$ 0	$ 0
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Two to Three Years from Balance Sheet Date	0.00%	0.00%
Maturing after three years through five years	$ 0	$ 0
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Three to Four Years from Balance Sheet Date	0.00%	0.00%
Maturing after five years	$ 189,000	$ 202,000
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, after Five Years from Balance Sheet Date	5.94%	5.94%
Total FHLB advances	$ 540,189,000	$ 202,000
Federal Home Loan Bank, advances, maximum outstanding at any month end	540,200,000	453,200,000
Federal Home Loan Bank, advances, average balance outstanding	$ 253,700,000	$ 151,300,000
Federal Home Loan Bank, Advances, Activity for Year, Average Interest Rate for Year	2.22%	1.26%
Federal Home Loan Bank, advances, average interest rate for year	2.64%	5.94%
Subsidiary, Banner Bank [Member]
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Federal Home Loan Bank, advances, percentage of total assets to support credit line	45.00%
Federal Home Loan Bank, advances, maximum credit line	$ 4,590,000,000
Subsidiary, Islanders Bank [Member]
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Federal Home Loan Bank, advances, percentage of total assets to support credit line	35.00%
Federal Home Loan Bank, advances, maximum credit line	$ 103,500,000

Federal Home Loan Bank, Advances, General Debt Obligations, Percentage of Total Assets to Support Credit Line

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- Definition

Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate Three to Five Years from Balance Sheet Date

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Federal Home Loan Bank, Advances, Maturities Summary, Due After One Year Through Three Years

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Federal Home Loan Bank, Advances, Maturities Summary, Due After Three Years Through Five Years

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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The calculated average balance outstanding for the year for all Federal Home Loan Bank advances as of the Balance Sheet date.

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The calculated weighted average interest rate for Federal Home Loan Bank advances for the period ended as of the Balance Sheet date.

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The maximum balance outstanding at any month end during the period as of the Balance Sheet date.

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
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Amount of maximum advances or credit lines available from the Federal Home Loan Bank (FHLB).

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Interest rate of advances made and reported by Federal Home Loan Bank (FHLBank).

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The weighted average interest rate applicable to the Federal Home Loan Bank advances which are due after five years of the Balance Sheet date.

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The weighted average interest rate applicable to the Federal Home Loan Bank advances which are due within one year of the Balance Sheet date.

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The weighted average interest rate applicable to the Federal Home Loan Bank advances which are due from two to three years of the Balance Sheet date.

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Amount of advances from Federal Home Loan Bank (FHLBank) maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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