XML 168 R152.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Equity (Details) - $ / shares | Feb. 09, 2024 | Nov. 13, 2023 | Aug. 14, 2023 | May 15, 2023 | Feb. 28, 2023 | Jan. 24, 2023
--- | --- | --- | --- | --- | --- | ---
Subsequent Event [Line Items] |  |  |  |  |  |
Cash dividends declared per common share (usd per share) |  | $ 0.36 | $ 0.36 | $ 0.36 |  | $ 0.35
Umpqua Bank and Columbia Banking System Merger |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |
Business Acquisition, Equity Interest Issued or Issuable, Share Exchange Ratio |  |  |  |  | 0.5958 |
Subsequent Event |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |
Cash dividends declared per common share (usd per share) | $ 0.36 |  |  |  |  |

X
- Definition Business Acquisition, Equity Interest Issued or Issuable, Share Exchange Ratio + References No definition available. + Details
Name: | colb_BusinessAcquisitionEquityInterestIssuedOrIssuableShareExchangeRatio
Namespace Prefix: | colb_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1 + Details
Name: | us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481674/830-30-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 855 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483399/855-10-50-2 + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=colb_UmpquaBankAndColumbiaBankingSystemMergerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |