Change in allowance for credit losses due to adoption of new ASU

No definition available.

Name:	colb_ChangeinallowanceforcreditlossesduetoadoptionofnewASU
Namespace Prefix:	colb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(2))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (c)

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (1)

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase in allowance for credit loss on financing receivable from recovery.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(4)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
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

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=colb_CommercialBusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=colb_AgricultureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=colb_OneToFourFamilyResidentialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_UnallocatedFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Allowance for Credit Losses and Unfunded Commitments and Letters of Credit (Allowance for Credit Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	$ 158,438	$ 155,578	$ 149,140		$ 83,968
Initial ACL recorded for PCD loans acquired		2,616
Financing Receivable, Allowance for Credit Loss, Writeoff	4,449	9,063	21,092
Financing Receivable, Allowance for Credit Loss, Recovery	5,359	8,085	6,932
Provision (recapture) for credit losses	1,950	4,800	77,700
Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	54,856	61,254	68,934		20,340
Initial ACL recorded for PCD loans acquired		2,225
Financing Receivable, Allowance for Credit Loss, Writeoff	299	1,044	1,419
Financing Receivable, Allowance for Credit Loss, Recovery	207	633	131
Provision (recapture) for credit losses	(6,306)	(9,494)	42,349
Commercial Business
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	57,836	54,712	45,250		30,292
Initial ACL recorded for PCD loans acquired		30
Financing Receivable, Allowance for Credit Loss, Writeoff	2,108	6,364	12,396
Financing Receivable, Allowance for Credit Loss, Recovery	2,183	4,862	3,438
Provision (recapture) for credit losses	3,049	10,934	23,154
Agriculture
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	9,071	8,148	9,052		15,835
Initial ACL recorded for PCD loans acquired		38
Financing Receivable, Allowance for Credit Loss, Writeoff	799	322	6,427
Financing Receivable, Allowance for Credit Loss, Recovery	869	355	172
Provision (recapture) for credit losses	853	(975)	8,797
Construction
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	13,142	5,397	7,636		8,571
Initial ACL recorded for PCD loans acquired		35
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0	0
Financing Receivable, Allowance for Credit Loss, Recovery	387	593	709
Provision (recapture) for credit losses	7,358	(2,867)	106
Real estate: One-to-four family residential
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	22,355	24,123	16,875		7,435
Initial ACL recorded for PCD loans acquired		286
Financing Receivable, Allowance for Credit Loss, Writeoff	3	170	84
Financing Receivable, Allowance for Credit Loss, Recovery	943	907	2,083
Provision (recapture) for credit losses	(2,708)	6,225	3,204
Consumer Loan
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss	1,178	1,944	1,393		883
Initial ACL recorded for PCD loans acquired		2
Financing Receivable, Allowance for Credit Loss, Writeoff	1,240	1,163	766
Financing Receivable, Allowance for Credit Loss, Recovery	770	735	399
Provision (recapture) for credit losses	$ (296)	977	99
Unallocated Financing Receivables [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for Credit Loss		0	0		$ 612
Initial ACL recorded for PCD loans acquired		0
Financing Receivable, Allowance for Credit Loss, Writeoff		0	0
Financing Receivable, Allowance for Credit Loss, Recovery		0	0
Provision (recapture) for credit losses		$ 0	$ (9)
Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				$ 1,632
Accounting Standards Update 2016-13 \| Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				7,533
Accounting Standards Update 2016-13 \| Commercial Business
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				762
Accounting Standards Update 2016-13 \| Agriculture
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				(9,325)
Accounting Standards Update 2016-13 \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				(1,750)
Accounting Standards Update 2016-13 \| Real estate: One-to-four family residential
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				4,237
Accounting Standards Update 2016-13 \| Consumer Loan
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				778
Accounting Standards Update 2016-13 \| Unallocated Financing Receivables [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Change in allowance for credit loss due to adoption of new ASU				$ (603)