Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Jan. 31, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Annual Report	true
Document Transition Report	false
Entity File Number	0-26584
Entity Registrant Name	BANNER CORPORATION
Entity Incorporation, State or Country Code	WA
Entity Tax Identification Number	91-1691604
Entity Address, Address Line One	10 South First Avenue
Entity Address, City or Town	Walla Walla
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	99362
City Area Code	509
Local Phone Number	527-3636
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	BANR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Amendment Flag	false
Entity Central Index Key	0000946673
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 1,478,884,667
Entity Common Stock, Shares Outstanding		34,348,455