XML 61 R51.htm IDEA: XBRL DOCUMENT v3.20.2

Loans - Narrative, Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) contract numberOfBorrowers	Jun. 30, 2019 contract	Jun. 30, 2020 USD ($) contract loan numberOfBorrowers	Jun. 30, 2019 USD ($) contract	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract)	4	0	3	2
Pre-Modification Outstanding Recorded Investment			$ 731	$ 2,836
Post-Modification Outstanding Recorded Investment			$ 731	$ 2,836
Number of borrowers | numberOfBorrowers	3		3
Troubled debt restructurings	$ 17,700		$ 17,700		$ 18,500
Number of TDR loans restructured that subsequently defaulted (contract) | contract			0	0
COVID-19
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-TDR loan restructuring modifications (contracts) | loan			262
Loans	345,900		$ 345,900
Deferred interest payback period, maximum			18 months
COVID-19 | Principal deferral (interest only)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-TDR loan restructuring modifications (contracts) | loan			60
Loans	142,500		$ 142,500
COVID-19 | Deferrable notes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-TDR loan restructuring modifications (contracts) | loan			202
Loans	$ 203,400		$ 203,400
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract) | loan			1
Pre-Modification Outstanding Recorded Investment			$ 187
Post-Modification Outstanding Recorded Investment			$ 187
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract) | contract				1
Pre-Modification Outstanding Recorded Investment				$ 2
Post-Modification Outstanding Recorded Investment				$ 2
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract)			2	1
Pre-Modification Outstanding Recorded Investment			$ 544	$ 2,834
Post-Modification Outstanding Recorded Investment			$ 544	$ 2,834

X

- Definition

Financing Receivable, Modification, Number Of Borrowers

+ References

No definition available.

+ Details

Name:	nfbk_FinancingReceivableModificationNumberOfBorrowers
Namespace Prefix:	nfbk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Financing Receivable, Non-TDR Modifications, Number of Contracts

+ References

No definition available.

+ Details

Name:	nfbk_FinancingReceivableNonTDRModificationsNumberofContracts
Namespace Prefix:	nfbk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Loan Modification Program, Deferred Interest Maximum Payback Period

+ References

No definition available.

+ Details

Name:	nfbk_LoanModificationProgramDeferredInterestMaximumPaybackPeriod
Namespace Prefix:	nfbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Trouble Debt Restructuring Amount.

+ References

No definition available.

+ Details

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

X

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

X

- Details

Name:	us-gaap_LoanRestructuringModificationNameAxis=nfbk_COVID19Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

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

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nfbk_ResidentialMember
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:

X

- Details

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