Business Combination, Purchase Price Allocation Amortizable Intangible Assets

No definition available.

Name:	colb_BusinessCombinationPurchasePriceAllocationAmortizableIntangibleAssets
Namespace Prefix:	colb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

+ References

No definition available.

+ Details

Name:	colb_BusinessCombinationPurchasePriceAllocationGoodwillAmount
Namespace Prefix:	colb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of acquired receivable from business combination, excluding certain loans and debt securities acquired in transfer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=128092470&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessCombinationAcquiredReceivablesFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI https://asc.fasb.org/extlink&oid=123586518&loc=d3e1043-128460

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount at purchase price of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919265-210447

+ Details

Name:	us-gaap_FinancingReceivablePurchasedWithCreditDeteriorationAmountAtPurchasePrice
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=colb_BankOfCommerceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=colb_UmpquaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Business Combinations and Asset Acquisitions - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 01, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Acquired PCD loans			$ 2,616
Bank of Commerce
Business Acquisition [Line Items]
Business Combination, Purchase Price Allocation, Goodwill Amount	$ 57,330
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	15,932
Business Combination, net loans acquired	1,084,984
Acquired PCD loans	$ 40,278
Business Combination, Acquisition Related Costs		$ 5,593	$ 10,370	$ 0
Umpqua
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$ 13,500