XML 63 R38.htm IDEA: XBRL DOCUMENT
v3.19.3

Accounting Pronouncements Recently Issued Narrative - Impact of implementation of new accounting standards (Details) - USD ($) $ in Thousands |  | 9 Months Ended |  |
--- | --- | --- | --- | ---
Jan. 01, 2020 | Sep. 30, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Accounting Standards Update 2016-02 [Member] |  |  |  |
Change in other assets due to adoption of new ASU |  | $ 49,200 |  |
Change in other liabilities due to adoption of new ASU |  | 48,200 |  |
Accounting Standards Update 2016-01 [Member] |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  | $ 0
Accounting Standards Update 2018-15 [Member] |  |  |  |
Change in other assets due to adoption of new ASU |  | $ 920 |  |
Retained Earnings [Member] | Accounting Standards Update 2016-02 [Member] |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  | $ 782 |
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member] |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  | $ (157)
Forecast [Member] | Minimum [Member] | Accounting Standards Update 2016-13 [Member] |  |  |  |
Estimated percentage change in allowance for credit losses | (10.00%) |  |  |
Forecast [Member] | Maximum [Member] | Accounting Standards Update 2016-13 [Member] |  |  |  |
Estimated percentage change in allowance for credit losses | 5.00% |  |  |

X
- Definition Change in other assets due to adoption of new ASU + References No definition available. + Details
Name: | colb_ChangeinotherassetsduetoadoptionofnewASU
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Change in other liabilities due to adoption of new ASU + References No definition available. + Details
Name: | colb_ChangeinotherliabilitiesduetoadoptionofnewASU
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Estimated percentage change in allowance for credit losses + References No definition available. + Details
Name: | colb_Estimatedpercentagechangeinallowanceforcreditlosses
Namespace Prefix: | colb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201601Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201815Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201613Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |