XML 67 R57.htm IDEA: XBRL DOCUMENT v3.21.2

Loans - Narrative, Collateral-Dependent Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Collateral-dependent impaired loans	$ 9,800	$ 10,200
Real estate loans: | Commercial mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Collateral-dependent impaired loans	7,700
Real estate loans: | Construction and land
Financing Receivable, Allowance for Credit Loss [Line Items]
Collateral-dependent impaired loans	1,100
Real estate loans: | Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Collateral-dependent impaired loans	619
Real estate loans: | One-to-Four Family
Financing Receivable, Allowance for Credit Loss [Line Items]
Collateral-dependent impaired loans	$ 380

X

- Definition

Financing Receivable, Impaired, Secured By Collateral

+ References

No definition available.

+ Details

Name:	nfbk_FinancingReceivableImpairedSecuredByCollateral
Namespace Prefix:	nfbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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