XML 45 R35.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Securities (Carrying Value of Securities Pledged as Collateral) (Details) $ in Thousands | Mar. 31, 2017 USD ($)
--- | ---
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | $ 409,299
Washington and Oregon State Public Deposits [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | 228,794
Federal Reserve Bank Advances [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | 54,551
Other Securities [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Carrying amount of securities pledged as collateral | $ 125,954

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=66008989&loc=d3e5086-111524 + Details
Name: | us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | colb_SecuritiesPledgedAsCollateralByCounterpartyAxis=colb_WashingtonAndOregonStatePublicDepositsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | colb_SecuritiesPledgedAsCollateralByCounterpartyAxis=us-gaap_FederalReserveBankAdvancesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | colb_SecuritiesPledgedAsCollateralByCounterpartyAxis=colb_OtherSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |