v2.4.1.9

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

X

- 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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- Details

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