v2.4.0.8

Fair Value Accounting and Measurement Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
--- | --- | ---
Assets |  |
Interest-earning deposits with banks | $ 14,531 | $ 389,353
Securities available for sale | 1,664,111 | 1,001,665
Reported Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 165,030 | 124,573
Interest-earning deposits with banks | 14,531 | 389,353
Securities available for sale | 1,664,111 | 1,001,665
FHLB stock | 32,529 | 21,819
Loans held for sale | 735 | 2,563
Loans | 4,444,842 | 2,864,803
FDIC loss-sharing asset | 39,846 | 96,354
Interest rate contracts | 9,044 | 14,921
Liabilities |  |
Deposits | 5,959,475 | 4,042,085
FHLB Advances | 36,606 | 6,644
Repurchase agreements | 25,000 | 25,000
Interest rate contracts | 9,044 | 14,921
Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 165,030 | 124,573
Interest-earning deposits with banks | 14,531 | 389,353
Securities available for sale | 1,664,111 | 1,001,665
FHLB stock | 32,529 | 21,819
Loans held for sale | 735 | 2,563
Loans | 4,605,038 | 2,944,317
FDIC loss-sharing asset | 11,248 | 26,543
Interest rate contracts | 9,044 | 14,921
Liabilities |  |
Deposits | 5,958,747 | 4,043,221
FHLB Advances | 35,080 | 5,894
Repurchase agreements | 26,361 | 26,464
Interest rate contracts | 9,044 | 14,921
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 0 | 0
Interest-earning deposits with banks | 0 | 0
Securities available for sale | 1,643,997 | 981,837
FHLB stock | 32,529 | 21,819
Loans held for sale | 735 | 2,563
Loans | 0 | 0
FDIC loss-sharing asset | 0 | 0
Interest rate contracts | 9,044 | 14,921
Liabilities |  |
Deposits | 509,201 | 493,400
FHLB Advances | 35,080 | 5,894
Repurchase agreements | 26,361 | 26,464
Interest rate contracts | 9,044 | 14,921
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 0 | 0
Interest-earning deposits with banks | 0 | 0
Securities available for sale | 0 | 0
FHLB stock | 0 | 0
Loans held for sale | 0 | 0
Loans | 4,605,038 | 2,944,317
FDIC loss-sharing asset | 11,248 | 26,543
Interest rate contracts | 0 | 0
Liabilities |  |
Deposits | 0 | 0
FHLB Advances | 0 | 0
Repurchase agreements | 0 | 0
Interest rate contracts | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 165,030 | 124,573
Interest-earning deposits with banks | 14,531 | 389,353
Securities available for sale | 20,114 | 19,828
FHLB stock | 0 | 0
Loans held for sale | 0 | 0
Loans | 0 | 0
FDIC loss-sharing asset | 0 | 0
Interest rate contracts | 0 | 0
Liabilities |  |
Deposits | 5,449,546 | 3,549,821
FHLB Advances | 0 | 0
Repurchase agreements | 0 | 0
Interest rate contracts | $ 0 | $ 0

X
- Definition FDIC Loss Sharing Asset Fair Value Disclosure + References No definition available. + Details
Name: | colb_FdicLossSharingAssetFairValue
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 + Details
Name: | us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References No definition available. + Details
Name: | us-gaap_DepositsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(3)(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.2) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6476743&loc=d3e59706-112781 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -Article 9 + Details
Name: | us-gaap_InterestBearingDepositsInBanks
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611 + Details
Name: | us-gaap_InterestRateDerivativeAssetsAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611 + Details
Name: | us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 20 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=29638263&loc=d3e39828-111592 + Details
Name: | us-gaap_InvestmentInFederalHomeLoanBankStockFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References No definition available. + Details
Name: | us-gaap_LoansHeldForSaleFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Glossary Loan -URI http://asc.fasb.org/extlink&oid=6517073 + Details
Name: | us-gaap_LoansReceivableFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611 + Details
Name: | us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant