v2.4.1.9

Securities (Carrying Value of Securities Pledged as Collateral) (Details) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015
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Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | $ 517,101 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
Washington and Oregon State Public Deposits [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | 323,771 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral / colb_SecuritiesPledgedAsCollateralByCounterpartyAxis = colb_WashingtonAndOregonStatePublicDepositsMember
Federal Reserve Bank Advances [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | 36,945 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral / colb_SecuritiesPledgedAsCollateralByCounterpartyAxis = us-gaap_FederalReserveBankAdvancesMember
Other Securities [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | $ 156,385 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral / colb_SecuritiesPledgedAsCollateralByCounterpartyAxis = colb_OtherSecuritiesMember

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- Definition The fair value of available-for-sale securities that serve as collateral for borrowings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5086-111524 + Details
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