Loans Receivable and Allowance for Credit Losses - Loans Modified (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount	$ 1,094	$ 5,445
% of Total Class of Loans Receivable	0.01%	0.07%
Commercial business loans \| Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount	$ 1,094	$ 5,445
% of Total Class of Loans Receivable	0.15%	0.89%
Commercial business loans \| Commercial business \| Minimum
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable, term extension	19 months	12 months
Commercial business loans \| Commercial business \| Maximum
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable, term extension	61 months	60 months
Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount		$ 673
Interest Rate Reduction \| Commercial business loans \| Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount		673
Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount	$ 494	2,000
Term Extension \| Commercial business loans \| Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount	494	2,000
Combination of Term Extension and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount	600	2,772
Combination of Term Extension and Interest Rate Reduction \| Commercial business loans \| Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modified in period, amount	$ 600	$ 2,772

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Percentage, excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=clbk_CommercialBusinessMember
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:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ContractualInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=clbk_CombinationOfTermExtensionInterestRateReductionAndPrincipalForgivenessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: