Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011
Document and Entity Information
Entity Registrant Name	Banner Corporation
Document Type	10-K
Document Period End Date	Dec. 31, 2011
Amendment Flag	false
Entity Central Index Key	0000946673
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding	17,519,132
Entity Public Float	$ 300,453,114
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY