XML 86 R76.htm IDEA: XBRL DOCUMENT
v3.20.2

Subsequent Events (Details) - Subsequent Event [Member] - USD ($) $ in Thousands, shares in Millions | Oct. 20, 2020 | Oct. 28, 2020
--- | --- | ---
Subsequent Event [Line Items] |  |
Stock Repurchase Program, Number of Shares Authorized to be Repurchased |  | 3.5
Stock Repurchase Program, Authorized Amount |  | $ 100,000
Gain on termination of interest rate collar | $ 34,900 |

X
- Definition Gain on termination of interest rate collar + References No definition available. + Details
Name: | colb_GainOnTerminationOfInterestRateCollar
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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 No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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