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

2,094colb_ImpairedLoansFinancialAssetsFairValue

OREO

1,429colb_OtherRealEstateOwnedFairValueDisclosure

6,125colb_OtherRealEstateOwnedFairValueDisclosure

Fair Value, Inputs, Level 3 [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items]

Impaired loans

2,094colb_ImpairedLoansFinancialAssetsFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
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OREO

1,429colb_OtherRealEstateOwnedFairValueDisclosure
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/ us-gaap_FairValueByMeasurementFrequencyAxis
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6,125colb_OtherRealEstateOwnedFairValueDisclosure
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/ 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

990colb_ImpairedLoansFinancialAssetsFairValue
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Other Collateral [Member] | Fair Value, Inputs, Level 3 [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items]

Impaired loans

1,104colb_ImpairedLoansFinancialAssetsFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ 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

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^[1],[2]

0.00%us-gaap_FairValueInputsComparabilityAdjustments
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/ 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
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/ colb_ReceivableByCollateralTypeAxis
= colb_OtherCollateralMember
/ us-gaap_ValuationTechniqueAxis
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^[1],[2]

100.00%us-gaap_FairValueInputsComparabilityAdjustments
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= colb_ImpairedLoansMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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^[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
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/ 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
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/ colb_ReceivableByCollateralTypeAxis
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^[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.

X

- Definition

Impaired Loans, Financial Assets, Fair Value

+ References

No definition available.

+ Details

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X

- Definition

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+ References

No definition available.

+ Details

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X

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X

- 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

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X

- Details

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X

- Details

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X

- Details

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