XML 58 R48.htm IDEA: XBRL DOCUMENT
v3.7.0.1

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
--- | ---
Mar. 31, 2017 | Mar. 31, 2016
Allowance For Loan And Lease Losses And Unfunded Loan Commitments And Letters Of Credit |  |
Beginning balance | $ 2,705 | $ 2,930
Allowance for Loan and Lease Losses, Net Changes In Unfunded Commitments and Letters Of Credit Allowance | 850 | 0
Ending balance | $ 3,555 | $ 2,930

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