Document and Entity Information Document	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	Banner Corporation
Document Type	10-Q
Document Period End Date	Sep. 30, 2013
Amendment Flag	false
Entity Central Index Key	0000946673
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		19,543,769
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3