v2.4.1.9

Fair Value Accounting and Measurement (Quantitative Information About Level 3 Fair Value Measurements) (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Impaired loans |  |  | 2,094 colb_ImpairedLoansFinancialAssetsFairValue |
OREO | 1,429 colb_OtherRealEstateOwnedFairValueDisclosure |  | 6,125 colb_OtherRealEstateOwnedFairValueDisclosure |
Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Impaired loans |  |  | 2,094 colb_ImpairedLoansFinancialAssetsFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |
OREO | 1,429 colb_OtherRealEstateOwnedFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  | 6,125 colb_OtherRealEstateOwnedFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |
Real Estate Collateral [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Impaired loans |  |  | 990 colb_ImpairedLoansFinancialAssetsFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / colb_ReceivableByCollateralTypeAxis = colb_RealEstateCollateralMember |
Other Collateral [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Impaired loans |  |  | 1,104 colb_ImpairedLoansFinancialAssetsFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember |
Other Collateral [Member] | Market Approach Valuation Technique [Member] | Impaired Loans [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Fair Value Inputs, Comparability Adjustments | 0.00%us-gaap_FairValueInputsComparabilityAdjustments / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = colb_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_MinimumMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember | [1],[2] | 0.00%us-gaap_FairValueInputsComparabilityAdjustments / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = colb_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_MinimumMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember | [1]
Other Collateral [Member] | Market Approach Valuation Technique [Member] | Impaired Loans [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Fair Value Inputs, Comparability Adjustments | 0.00%us-gaap_FairValueInputsComparabilityAdjustments / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = colb_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_MaximumMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember | [1],[2] | 100.00%us-gaap_FairValueInputsComparabilityAdjustments / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = colb_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_MaximumMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember | [1]
Other Collateral [Member] | Market Approach Valuation Technique [Member] | Impaired Loans [Member] | Weighted Average [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |
Fair Value Inputs, Comparability Adjustments | 0.00%us-gaap_FairValueInputsComparabilityAdjustments / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = colb_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember | [1],[2] | 68.00%us-gaap_FairValueInputsComparabilityAdjustments / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = colb_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / colb_ReceivableByCollateralTypeAxis = colb_OtherCollateralMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember | [1],[2]
[1] | Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
[2] | Other collateral consists of accounts receivable and inventory.

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- Definition Impaired Loans, Financial Assets, Fair Value + References No definition available. + Details
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Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Other Real Estate Owned, Fair Value Disclosure + References No definition available. + Details
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Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition Percentage of adjustment to the observed price for a similar asset or liability when an identical transaction does not exist, used as an input to measure fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |