Fair Value Measurements - Qualitative Valuation (Details) $ in Thousands	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Measured on non-recurring basis
Fair Value
Impaired loans		$ 1,213
Mortgage servicing rights	$ 1,980	1,906
Significant Unobservable Inputs (Level 3)
Fair Value
Impaired loans	6,249,831	6,457,766
Significant Unobservable Inputs (Level 3) \| Measured on non-recurring basis
Fair Value
Impaired loans		1,213
Mortgage servicing rights	$ 1,980	$ 1,906
Significant Unobservable Inputs (Level 3) \| Discount rate \| Measured on non-recurring basis \| Estimated Cash Flow
Unobservable Inputs
Impaired loans		0
Significant Unobservable Inputs (Level 3) \| Discount rate \| Measured on non-recurring basis \| Weighted Average \| Estimated Cash Flow
Unobservable Inputs
Impaired loans		0
Significant Unobservable Inputs (Level 3) \| Discount rate \| Measured on non-recurring basis \| Weighted Average \| Discounted cash flow
Unobservable Inputs
Mortgage servicing rights	0.1050	0.1025
Significant Unobservable Inputs (Level 3) \| Prepayment speeds and discount rates \| Measured on non-recurring basis \| Minimum \| Discounted cash flow
Unobservable Inputs
Mortgage servicing rights	0.058	0.075
Significant Unobservable Inputs (Level 3) \| Prepayment speeds and discount rates \| Measured on non-recurring basis \| Maximum \| Discounted cash flow
Unobservable Inputs
Mortgage servicing rights	0.240	0.249
Significant Unobservable Inputs (Level 3) \| Prepayment speeds and discount rates \| Measured on non-recurring basis \| Weighted Average \| Discounted cash flow
Unobservable Inputs
Mortgage servicing rights	0.108	0.127

Fair Value Measurement Inputs And Valuation Techniques, Fair Value

No definition available.

Name:	clbk_FairValueMeasurementInputsAndValuationTechniquesFairValueAbstract
Namespace Prefix:	clbk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair Value Measurement Inputs And Valuation Techniques, Unobservable Inputs

+ References

No definition available.

+ Details

Name:	clbk_FairValueMeasurementInputsAndValuationTechniquesUnobservableInputsAbstract
Namespace Prefix:	clbk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Impaired Financing Receivable, Measurement Input

+ References

No definition available.

+ Details

Name:	clbk_ImpairedFinancingReceivableMeasurementInput
Namespace Prefix:	clbk_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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

- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=125521744&loc=d3e122625-111746

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

+ Details

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

- Definition

Value of input used to measure servicing asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_ServicingAssetMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=clbk_EstimatedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueDiscountedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=clbk_MeasurementInputPrepaymentsSpeedsAndDiscountRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: