Document and Entity Information (USD $)	3 Months Ended
	Mar. 31, 2012
Document and Entity Information
Entity Registrant Name	Banner Corporation
Document Type	10-Q
Document Period End Date	Mar. 31, 2012
Amendment Flag	false
Entity Central Index Key	0000946673
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding	17,993,428
Entity Public Float	$ 396,395,219
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1