v2.4.1.9

Loans (Analysis of Nonaccrual Loans) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	$ 31,828us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus	$ 31,352us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Unpaid Principal Balance Nonaccrual Loans	37,798colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus	44,774colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	2,868us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember	2,939us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Unpaid Principal Balance Nonaccrual Loans	3,799colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember	3,930colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	17,240us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_SecuredLoansMember	16,552us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_SecuredLoansMember
Unpaid Principal Balance Nonaccrual Loans	20,573colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_SecuredLoansMember	21,453colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_SecuredLoansMember
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	189us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_UnsecuredLoansMember	247us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_UnsecuredLoansMember
Unpaid Principal Balance Nonaccrual Loans	211colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_UnsecuredLoansMember	269colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_UnsecuredLoansMember
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	4,429us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OneToFourFamilyResidentialMember	2,822us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OneToFourFamilyResidentialMember
Unpaid Principal Balance Nonaccrual Loans	6,109colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OneToFourFamilyResidentialMember	5,680colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OneToFourFamilyResidentialMember
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	1,616us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_CommercialLandMember	821us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_CommercialLandMember
Unpaid Principal Balance Nonaccrual Loans	1,560colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_CommercialLandMember	1,113colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_CommercialLandMember
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	887us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_IncomePropertyMultifamilyMember	3,200us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_IncomePropertyMultifamilyMember
Unpaid Principal Balance Nonaccrual Loans	887colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_IncomePropertyMultifamilyMember	5,521colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_IncomePropertyMultifamilyMember
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	1,995us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedMember	3,826us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedMember
Unpaid Principal Balance Nonaccrual Loans	2,036colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedMember	5,837colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedMember
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	871us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_LandAndAcquisitionMember	95us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_LandAndAcquisitionMember
Unpaid Principal Balance Nonaccrual Loans	871colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_LandAndAcquisitionMember	112colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_LandAndAcquisitionMember
Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	1,263us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_ResidentialConstructionMember	370us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_ResidentialConstructionMember
Unpaid Principal Balance Nonaccrual Loans	1,263colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_ResidentialConstructionMember	370colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_ResidentialConstructionMember
Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment Nonaccrual Loans	470us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedConstructionMember
Unpaid Principal Balance Nonaccrual Loans	$ 489colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedConstructionMember	$ 489colb_FinancingReceivableUnpaidPrincipalBalanceNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = colb_OwnerOccupiedConstructionMember

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+ References

No definition available.

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- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524

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