XML 104 R78.htm IDEA: XBRL DOCUMENT
v3.20.4

Other Real Estate Owned (Narrative) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Other Real Estate Owned [Line Items] |  |  |
Foreclosed residential real estate properties | $ 553 | $ 552 | $ 6,019
Mortgage Loans in Process of Foreclosure, Amount | 260 |  |
Real estate: One-to-four family residential |  |  |
Other Real Estate Owned [Line Items] |  |  |
Foreclosed residential real estate properties | $ 0 |  |

X
- Definition Other Real Estate Owned [Line Items] + References No definition available. + Details
Name: | colb_OtherRealEstateOwnedLineItems
Namespace Prefix: | colb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 35 -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL49126937-111524 + Details
Name: | us-gaap_MortgageLoansInProcessOfForeclosureAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5162-111524 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4437-111522 + Details
Name: | us-gaap_RealEstateAcquiredThroughForeclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=colb_OneToFourFamilyResidentialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |