XML 67 R54.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Changes in the Allowance for Unfunded Commitments and Letters of Credit) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Allowance For Loan And Lease Losses And Unfunded Loan Commitments And Letters Of Credit |  |  |  |
Beginning balance | $ 4,330 | $ 3,555 | $ 3,130 | $ 2,705
Allowance for Loan and Lease Losses, Net Changes In Unfunded Commitments and Letters Of Credit Allowance | (650) | 0 | 550 | 850
Ending balance | $ 3,680 | $ 3,555 | $ 3,680 | $ 3,555

X
- Definition Allowance For Loan And Lease Losses And Unfunded Loan Commitments And Letters Of Credit [Abstract] + References No definition available. + Details
Name: | colb_AllowanceForLoanAndLeaseLossesAndUnfundedLoanCommitmentsAndLettersOfCredit
Namespace Prefix: | colb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Allowance for Loan and Lease Losses, Net Changes In Unfunded Commitments and Letters Of Credit Allowance + References No definition available. + Details
Name: | colb_AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Allowance For Unfunded Loan Commitments And Letters Of Credit + References No definition available. + Details
Name: | colb_AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant