XML 45 R43.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans (Analysis of Loan Portfolio by Major Types of Loans) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]        
Less: Unearned income on loans $ (53,867)us-gaap_LoansAndLeasesReceivableDeferredIncome $ (59,374)us-gaap_LoansAndLeasesReceivableDeferredIncome    
Recorded Investment 5,450,895us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome 5,445,378us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome    
Allowance for loan losses (70,234)us-gaap_LoansAndLeasesReceivableAllowance (69,569)us-gaap_LoansAndLeasesReceivableAllowance (70,571)us-gaap_LoansAndLeasesReceivableAllowance (72,454)us-gaap_LoansAndLeasesReceivableAllowance
Loans, net 5,380,661us-gaap_LoansAndLeasesReceivableNetReportedAmount 5,375,809us-gaap_LoansAndLeasesReceivableNetReportedAmount    
Loans held for sale 3,545us-gaap_LoansReceivableHeldForSaleNet 1,116us-gaap_LoansReceivableHeldForSaleNet    
Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Less: Unearned income on loans (53,867)us-gaap_LoansAndLeasesReceivableDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
(59,374)us-gaap_LoansAndLeasesReceivableDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Recorded Investment 5,231,056us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
5,214,794us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Allowance for loan losses (53,703)us-gaap_LoansAndLeasesReceivableAllowance
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
(53,233)us-gaap_LoansAndLeasesReceivableAllowance
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans, net 5,177,353us-gaap_LoansAndLeasesReceivableNetReportedAmount
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
5,161,561us-gaap_LoansAndLeasesReceivableNetReportedAmount
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans held for sale 3,545us-gaap_LoansReceivableHeldForSaleNet
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
1,116us-gaap_LoansReceivableHeldForSaleNet
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 5,231,056us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
5,214,794us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Less: Unearned income on loans 0us-gaap_LoansAndLeasesReceivableDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
0us-gaap_LoansAndLeasesReceivableDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Recorded Investment 219,839us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
230,584us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Allowance for loan losses (16,531)us-gaap_LoansAndLeasesReceivableAllowance
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
(16,336)us-gaap_LoansAndLeasesReceivableAllowance
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans, net 203,308us-gaap_LoansAndLeasesReceivableNetReportedAmount
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
214,248us-gaap_LoansAndLeasesReceivableNetReportedAmount
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans held for sale 0us-gaap_LoansReceivableHeldForSaleNet
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
0us-gaap_LoansReceivableHeldForSaleNet
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 243,111us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
256,468us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Acquisition Accounting Valuation Discount on Covered Loans 23,272colb_AcquisitionAccountingValuationDiscountOnCoveredLoans
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
25,884colb_AcquisitionAccountingValuationDiscountOnCoveredLoans
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Commercial and Multifamily Residential Construction [Domain] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross 2,501us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialandMultifamilyResidentialConstructionDomain
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
2,588us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialandMultifamilyResidentialConstructionDomain
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
One-to-Four Family Residential [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross, Consumer, Mortgage 200,340us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
202,564us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
   
Loans and Leases Receivable, Gross, Consumer, Construction 127,814us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
120,887us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
   
Allowance for loan losses (1,364)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
(2,281)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
(1,194)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
(1,252)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
One-to-Four Family Residential [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross, Consumer, Mortgage 173,739us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
175,571us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross, Consumer, Construction 124,017us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
116,866us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 170,307us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
171,764us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
One-to-Four Family Residential [Member] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross, Consumer, Mortgage 26,601us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
26,993us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross, Consumer, Construction 3,797us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
4,021us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 31,127us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
31,981us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Commercial and Multifamily Residential [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable, Gross, Commercial, Mortgage 2,492,684us-gaap_LoansReceivableCommercialMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
2,492,310us-gaap_LoansReceivableCommercialMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
   
Loans Receivable, Gross, Commercial, Construction 122,118us-gaap_LoansReceivableCommercialConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
136,764us-gaap_LoansReceivableCommercialConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
   
Commercial and Multifamily Residential [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable, Gross, Commercial, Mortgage 2,374,454us-gaap_LoansReceivableCommercialMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
2,363,541us-gaap_LoansReceivableCommercialMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans Receivable, Gross, Commercial, Construction 119,880us-gaap_LoansReceivableCommercialConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
134,443us-gaap_LoansReceivableCommercialConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Commercial and Multifamily Residential [Member] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable, Gross, Commercial, Mortgage 118,230us-gaap_LoansReceivableCommercialMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
128,769us-gaap_LoansReceivableCommercialMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans Receivable, Gross, Commercial, Construction 2,238us-gaap_LoansReceivableCommercialConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
2,321us-gaap_LoansReceivableCommercialConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 127,952us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
140,398us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_CommercialAndMultifamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Commercial Portfolio Segment [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable, Gross, Commercial and Industrial 2,186,208us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
2,164,070us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Commercial Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable, Gross, Commercial and Industrial 2,139,873us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
2,119,565us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Commercial Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable, Gross, Commercial and Industrial 46,335us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
44,505us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 52,115us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
50,334us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Real Estate Portfolio Segment [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable Real Estate Mortgage 2,693,024colb_LoansReceivableRealEstateMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
2,694,874colb_LoansReceivableRealEstateMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
   
Real Estate Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable Real Estate Mortgage 2,548,193colb_LoansReceivableRealEstateMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
2,539,112colb_LoansReceivableRealEstateMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Real Estate Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable Real Estate Mortgage 144,831colb_LoansReceivableRealEstateMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
155,762colb_LoansReceivableRealEstateMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 159,079us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
172,379us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstatePortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
One-to-Four Family Residential Construction [Domain] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross 4,026us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OnetoFourFamilyResidentialConstructionDomain
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
4,353us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_OnetoFourFamilyResidentialConstructionDomain
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Real Estate Construction Portfolio Segment [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable Real Estate Construction 249,932colb_LoansReceivableRealEstateConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
257,651colb_LoansReceivableRealEstateConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
   
Real Estate Construction Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable Real Estate Construction 243,897colb_LoansReceivableRealEstateConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
251,309colb_LoansReceivableRealEstateConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Real Estate Construction Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans Receivable Real Estate Construction 6,035colb_LoansReceivableRealEstateConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
6,342colb_LoansReceivableRealEstateConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 6,527us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
6,941us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= colb_RealEstateConstructionPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Consumer Portfolio Segment [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross, Consumer 375,598us-gaap_LoansAndLeasesReceivableConsumer
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
388,157us-gaap_LoansAndLeasesReceivableConsumer
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Allowance for loan losses (2,835)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
(3,180)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
(2,637)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
(2,547)us-gaap_LoansAndLeasesReceivableAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Consumer Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross, Consumer 352,960us-gaap_LoansAndLeasesReceivableConsumer
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
364,182us-gaap_LoansAndLeasesReceivableConsumer
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross 336,158us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
345,032us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember
   
Consumer Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]        
Financing Receivable, Recorded Investment [Line Items]        
Loans and Leases Receivable, Gross, Consumer 22,638us-gaap_LoansAndLeasesReceivableConsumer
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
23,975us-gaap_LoansAndLeasesReceivableConsumer
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
   
Loans and Leases Receivable, Gross $ 25,390us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember
$ 26,814us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ colb_LoansByMajorCategoryAxis
= colb_PurchasedCreditImpairedLoansMember