BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Textuals) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) office	Dec. 31, 2020 USD ($)
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Gain (Loss) on Sales of Loans, Net	$ 34,500	$ 51,900
Not Designated as Hedging Instrument [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Derivative Asset, Notional Amount	695,678	671,564
Designated as Hedging Instrument [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Derivative Asset, Notional Amount	$ 0	338
Subsidiary, Banner Bank [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Number of offices | office	150
Number of production offices | office	18
Minimum [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Intangible asset, useful life	8 years
Minimum [Member] | Core Deposit Intangibles [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Intangible asset, useful life	8 years
Maximum [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Intangible asset, useful life	10 years
Maximum [Member] | Core Deposit Intangibles [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Intangible asset, useful life	10 years
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Derivative Asset, Notional Amount	$ 551,606	$ 451,760
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Derivative Asset, Notional Amount	$ 400,000