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Loans Loans (Analysis of Troubled Debt Restructurings) (Details) (USD $)
In Thousands, unless otherwise specified
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3 Months Ended |
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Mar. 31, 2015
Modifications
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Mar. 31, 2014
Modifications
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Dec. 31, 2014
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| Financing Receivable, Modifications [Line Items] |
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|
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| Financing Receivable Modifications Additional Commitment To Lend |
0colb_FinancingReceivableModificationsAdditionalCommitmentToLend |
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$ 0colb_FinancingReceivableModificationsAdditionalCommitmentToLend |
| Loans, Excluding Purchased Credit Impaired Loans [Member] |
|
|
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| Financing Receivable, Modifications [Line Items] |
|
|
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| Number of TDR Modifications |
0colb_FinancingReceivableModificationsNumberOfContractsDuration
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
5colb_FinancingReceivableModificationsNumberOfContractsDuration
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Pre-Modification Outstanding Recorded Investment |
|
1,183colb_FinancingReceivableModificationsPreModificationRecordedInvestmentDuration
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Post-Modification Outstanding Recorded Investment |
|
1,166colb_FinancingReceivableModificationsPostModificationRecordedInvestmentDuration
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Loans, Excluding Purchased Credit Impaired Loans [Member] | Secured Loans [Member] |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
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| Number of TDR Modifications |
|
2colb_FinancingReceivableModificationsNumberOfContractsDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_SecuredLoansMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Pre-Modification Outstanding Recorded Investment |
|
546colb_FinancingReceivableModificationsPreModificationRecordedInvestmentDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_SecuredLoansMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Post-Modification Outstanding Recorded Investment |
|
546colb_FinancingReceivableModificationsPostModificationRecordedInvestmentDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_SecuredLoansMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Loans, Excluding Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member] |
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|
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| Financing Receivable, Modifications [Line Items] |
|
|
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| Number of TDR Modifications |
|
2colb_FinancingReceivableModificationsNumberOfContractsDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Pre-Modification Outstanding Recorded Investment |
|
494colb_FinancingReceivableModificationsPreModificationRecordedInvestmentDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Post-Modification Outstanding Recorded Investment |
|
494colb_FinancingReceivableModificationsPostModificationRecordedInvestmentDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_OneToFourFamilyResidentialMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
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| Loans, Excluding Purchased Credit Impaired Loans [Member] | Income Property Multifamily [Member] |
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| Financing Receivable, Modifications [Line Items] |
|
|
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| Number of TDR Modifications |
|
1colb_FinancingReceivableModificationsNumberOfContractsDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_IncomePropertyMultifamilyMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Pre-Modification Outstanding Recorded Investment |
|
143colb_FinancingReceivableModificationsPreModificationRecordedInvestmentDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_IncomePropertyMultifamilyMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|
| Post-Modification Outstanding Recorded Investment |
|
$ 126colb_FinancingReceivableModificationsPostModificationRecordedInvestmentDuration
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= colb_IncomePropertyMultifamilyMember
/ colb_LoansByMajorCategoryAxis
= colb_LoansExcludingPurchasedCreditImpairedLoansMember |
|