Schedule H, Part IV, Line 4i - Schedule of Assets (Held at End of Year) (Details) - EBP 002 - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
EBP, Schedule of Asset Held for Investment [Line Items]
Entity tax identification number	13-5578494
Plan number	002
Current Value	$ 43,438
Notes receivable from participants, current value	830
Mutual funds
EBP, Schedule of Asset Held for Investment [Line Items]
Current Value	36,522
Common collective trust funds
EBP, Schedule of Asset Held for Investment [Line Items]
Current Value	1,313
Principal Life Insurance Company
EBP, Schedule of Asset Held for Investment [Line Items]
Current Value	$ 577
Common Stock of Northfield Bancorp, Inc.
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	281,962	302,947
Current Value	$ 3,223
Self-directed brokerage account
EBP, Schedule of Asset Held for Investment [Line Items]
Current Value	$ 1,803
Minimum
EBP, Schedule of Asset Held for Investment [Line Items]
Notes receivable from participants, interest rate	3.25%
Maximum
EBP, Schedule of Asset Held for Investment [Line Items]
Notes receivable from participants, interest rate	8.50%
Investment, Identifier [Axis]: Common/Collective Trusts \| International Growth Fund II
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	22,640
Current Value	$ 369
Investment, Identifier [Axis]: Common/Collective Trusts \| Pioneer Bond Fund Trust
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	15,898
Current Value	$ 197
Investment, Identifier [Axis]: Common/Collective Trusts \| Wilmington Trust Collective Investment Trust Large Cap
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	28,717
Current Value	$ 747
Investment, Identifier [Axis]: Guaranteed Annuity Contract \| Northfield Bancorp, Inc. Common Stock
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	281,962
Investment, Identifier [Axis]: Mutual funds \| Calvert US Large Cap Core Responsible Index Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	8,814
Current Value	$ 493
Investment, Identifier [Axis]: Mutual funds \| Fidelity 500 Index Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	12,697
Current Value	$ 3,018
Investment, Identifier [Axis]: Mutual funds \| Fidelity Emerging Markets Index Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	18,821
Current Value	$ 258
Investment, Identifier [Axis]: Mutual funds \| Fidelity International Index Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	6,747
Current Value	$ 410
Investment, Identifier [Axis]: Mutual funds \| Fidelity Mid Cap Index Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	16,628
Current Value	$ 614
Investment, Identifier [Axis]: Mutual funds \| Fidelity Small Cap Index Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	17,700
Current Value	$ 548
Investment, Identifier [Axis]: Mutual funds \| Fidelity US Bond Index
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	19,257
Current Value	$ 203
Investment, Identifier [Axis]: Mutual funds \| JPMorgan Large Cap Growth Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	21,184
Current Value	$ 1,831
Investment, Identifier [Axis]: Mutual funds \| Lord Abbett Bond-Debenture Fund Inc
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	20,480
Current Value	$ 149
Investment, Identifier [Axis]: Mutual funds \| Nuveen Lifecycle Index 2015 Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	27,399
Current Value	$ 487
Investment, Identifier [Axis]: Mutual funds \| Nuveen Lifecycle Index Retirement Income Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	15,898
Current Value	$ 277
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2020 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	37,978
Current Value	$ 758
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2025 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	150,896
Current Value	$ 3,475
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2030 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	194,475
Current Value	$ 5,216
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2035 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	119,071
Current Value	$ 3,596
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2040 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	153,821
Current Value	$ 5,155
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2045 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	74,510
Current Value	$ 2,676
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2050 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	58,801
Current Value	$ 2,167
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2055 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	60,984
Current Value	$ 1,828
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2060 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	75,633
Current Value	$ 1,766
Investment, Identifier [Axis]: Mutual funds \| TIAA-CREF Lifecycle Index 2065 Institutional Fund
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	30,873
Current Value	$ 518
Investment, Identifier [Axis]: Mutual funds \| Vanguard Federal Money Market
EBP, Schedule of Asset Held for Investment [Line Items]
Description of Investment Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value (in shares)	1,079,435
Current Value	$ 1,079

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

+ Details

Name:	dei_EntityTaxIdentificationNumber
Namespace Prefix:	dei_
Data Type:	dei:employerIdItemType
Balance Type:	na
Period Type:	duration

- Definition

Current value of investment, excluding plan interest in master trust, in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract.

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after deemed distribution, of participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of shares or units of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (3)
-Publisher DOL-EBSA

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (4)
-Publisher DOL-EBSA

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(B)
-Publisher DOL-EBSA

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (2)(i)(B)
-Publisher DOL-EBSA

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 6
-Paragraph d
-Subparagraph (1)(ii)
-Publisher DOL-EBSA

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-02(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanInvestmentNumberOfShares
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Interest rate on participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Plan number of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), in three-digit numeric format.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule II))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)
-Publisher DOL-EBSA

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule III))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (3)
-Publisher DOL-EBSA

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (4)
-Publisher DOL-EBSA

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 6
-Paragraph d
-Subparagraph (1)
-Publisher DOL-EBSA

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 6
-Paragraph d
-Subparagraph (2)
-Publisher DOL-EBSA

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (2)
-Publisher DOL-EBSA

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanPlanNumber
Namespace Prefix:	us-gaap-ebp_
Data Type:	us-types:threeDigitItemType
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/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(D)
-Publisher DOL-EBSA

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(A)
-Publisher DOL-EBSA

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(C)
-Publisher DOL-EBSA

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(B)
-Publisher DOL-EBSA

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration