    <SEC-DOCUMENT>0000887343-18-000010-index.html : 20180126
    <SEC-HEADER>0000887343-18-000010.hdr.sgml : 20180126
    <ACCEPTANCE-DATETIME>20180125193934
    ACCESSION NUMBER:		0000887343-18-000010
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		3
    CONFORMED PERIOD OF REPORT:	20180125
    ITEM INFORMATION:		Results of Operations and Financial Condition
    ITEM INFORMATION:		Other Events
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20180126
    DATE AS OF CHANGE:		20180125

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			COLUMBIA BANKING SYSTEM INC
    		CENTRAL INDEX KEY:			0000887343
    		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
    		IRS NUMBER:				911422237
    		STATE OF INCORPORATION:			WA
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-20288
    		FILM NUMBER:		18549613

    	BUSINESS ADDRESS:
    		STREET 1:		1301 A STREET
    		CITY:			TACOMA
    		STATE:			WA
    		ZIP:			98402
    		BUSINESS PHONE:		2533051900

    	MAIL ADDRESS:
    		STREET 1:		1301 A STREET
    		CITY:			TACOMA
    		STATE:			WA
    		ZIP:			98402
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>colb4q2017form8-k.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: colb4q2017form8-k.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>2
    <FILENAME>a991colb4q2017earningsrele.htm
    <DESCRIPTION>PRESS RELEASE - EARNINGS AND DIVIDEND
    <TEXT>
    Document 2 - file: a991colb4q2017earningsrele.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>cbsystemsolidbuga03.jpg
    <DESCRIPTION>LOGO
    <TEXT>
    Document 3 - file: cbsystemsolidbuga03.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>