$NFBK
Northfield Bancorp, Inc. Stock $nfbk

$nfbk Overview Financials Valuation SEC Filings Company Website

2024 Q1 Form 10-K Financial Statement

#000149322524000059 Filed on February 29, 2024

Income Statement

Concept	2024 Q1	2023 Q4	2023
Revenue	$1.615M		$5.479M
YoY Change	17.03%		-3.96%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$943.0K	$942.0K	$3.700M
YoY Change	0.32%	0.86%	2.78%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$30.76M		$84.13M
YoY Change	104.67%		293.45%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$8.518M	$11.29M	$51.76M
YoY Change	-47.54%	-42.6%	-39.0%
Income Tax	$2.304M	$3.072M	$14.09M
% Of Pretax Income	27.05%	27.2%	27.22%
Net Earnings	$6.214M	$8.222M	$37.67M
YoY Change	-46.92%	-41.85%	-38.37%
Net Earnings / Revenue	384.77%		687.52%
Basic Earnings Per Share	$0.15		$0.86
Diluted Earnings Per Share	$0.15	$0.19	$0.86
COMMON SHARES
Basic Shares Outstanding	44.46M shares	44.96M shares	43.56M shares
Diluted Shares Outstanding	42.41M shares		43.64M shares

Balance Sheet

Concept	2024 Q1	2023 Q4	2023
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$238.8M	$229.5M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$54.38M	$54.97M	$54.97M
YoY Change	120.38%	-7.03%	-7.03%
Goodwill	$41.01M	$41.00M
YoY Change	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets
YoY Change
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$5.852B	$5.598B	$5.598B
YoY Change	3.33%	-0.05%	-0.05%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$30.20M	$25.10M	$25.10M
YoY Change	-2.09%	-3.44%	-3.44%
Accrued Expenses	$75.76M	$74.92M	$74.92M
YoY Change	-1.14%	-4.96%	-4.96%
Deferred Revenue
YoY Change
Short-Term Debt	$25.00M	$25.00M	$25.00M
YoY Change	0.0%	0.0%	0.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$131.0M	$125.0M	$125.0M
YoY Change	-1.15%	19.27%	19.27%
LONG-TERM LIABILITIES
Long-Term Debt	$1.101B	$895.5M	$895.5M
YoY Change	11.76%	44.47%	44.47%
Other Long-Term Liabilities
YoY Change
Total Long-Term Liabilities	$1.101B	$895.5M	$895.5M
YoY Change	11.76%	44.47%	44.47%
TOTAL LIABILITIES
Total Short-Term Liabilities	$131.0M	$125.0M	$125.0M
Total Long-Term Liabilities	$1.101B	$895.5M	$895.5M
Total Liabilities	$5.153B	$4.899B	$4.899B
YoY Change	3.79%	-0.02%	-0.02%
SHAREHOLDERS EQUITY
Retained Earnings	$433.9M	$433.2M
YoY Change	2.29%	3.56%
Common Stock	$648.0K	$648.0K
YoY Change	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$698.4M	$699.4M	$699.4M
YoY Change
Total Liabilities & Shareholders Equity	$5.852B	$5.598B	$5.598B
YoY Change	3.33%	-0.05%	-0.05%

Cashflow Statement

Concept	2024 Q1	2023 Q4	2023
OPERATING ACTIVITIES
Net Income	$6.214M	$8.222M	$37.67M
YoY Change	-46.92%	-41.85%	-38.37%
Depreciation, Depletion And Amortization	$943.0K	$942.0K	$3.700M
YoY Change	0.32%	0.86%	2.78%
Cash From Operating Activities	$4.237M	$14.29M	$46.97M
YoY Change	-76.13%	-42.77%	-43.63%
INVESTING ACTIVITIES
Capital Expenditures	$451.0K	$1.525M	$3.605M
YoY Change	-38.97%	333.24%	41.26%
Acquisitions
YoY Change
Other Investing Activities	-$239.0M	-$3.206M	$197.5M
YoY Change	-568.8%	-107.72%	-171.12%
Cash From Investing Activities	-$239.4M	-$4.731M	$193.9M
YoY Change	-576.6%	-111.49%	-169.19%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	$244.5M	139.4M	-$57.13M
YoY Change	441.25%	-253.17%	-137.68%
NET CHANGE
Cash From Operating Activities	$4.237M	14.29M	$46.97M
Cash From Investing Activities	-$239.4M	-4.731M	$193.9M
Cash From Financing Activities	$244.5M	139.4M	-$57.13M
Net Change In Cash	$9.275M	149.0M	$183.7M
YoY Change	-91.8%	-699.04%	-505.81%
FREE CASH FLOW
Cash From Operating Activities	$4.237M	$14.29M	$46.97M
Capital Expenditures	$451.0K	$1.525M	$3.605M
Free Cash Flow	$3.786M	$12.77M	$43.37M
YoY Change	-77.75%	-48.15%	-46.32%

Facts In Submission

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CY2023	dei	Entity File Number EntityFileNumber	001-35791
CY2023	dei	Entity Registrant Name EntityRegistrantName	Northfield Bancorp, Inc.
CY2023	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2023	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	80-0882592
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CY2023	dei	Entity Address City Or Town EntityAddressCityOrTown	Woodbridge,
CY2023	dei	Entity Address State Or Province EntityAddressStateOrProvince	NJ
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CY2022	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	279000	usd
CY2021	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	1495000	usd
CY2023	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1721000	usd
CY2022	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-2206000	usd
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1703000	usd
CY2023	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	134000	usd
CY2022	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	453000	usd
CY2021	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1401000	usd
CY2023	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	948000	usd
CY2022	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	338000	usd
CY2021	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	357000	usd
CY2023	us-gaap	Noninterest Income NoninterestIncome	11896000	usd
CY2022	us-gaap	Noninterest Income NoninterestIncome	7983000	usd
CY2021	us-gaap	Noninterest Income NoninterestIncome	14453000	usd
CY2023	us-gaap	Labor And Related Expense LaborAndRelatedExpense	46496000	usd
CY2022	us-gaap	Labor And Related Expense LaborAndRelatedExpense	41961000	usd
CY2021	us-gaap	Labor And Related Expense LaborAndRelatedExpense	43677000	usd
CY2022	us-gaap	Professional Fees ProfessionalFees	3846000	usd
CY2021	us-gaap	Professional Fees ProfessionalFees	3596000	usd
CY2023	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2171000	usd
CY2023	us-gaap	Occupancy Net OccupancyNet	13259000	usd
CY2022	us-gaap	Occupancy Net OccupancyNet	13241000	usd
CY2021	us-gaap	Occupancy Net OccupancyNet	13956000	usd
CY2023	us-gaap	Equipment Expense EquipmentExpense	1868000	usd
CY2022	us-gaap	Equipment Expense EquipmentExpense	1730000	usd
CY2021	us-gaap	Equipment Expense EquipmentExpense	1737000	usd
CY2023	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	8138000	usd
CY2022	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	7415000	usd
CY2021	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	6784000	usd
CY2022	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2159000	usd
CY2021	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2358000	usd
CY2023	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	2331000	usd
CY2022	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1407000	usd
CY2021	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1365000	usd
CY2023	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	-555000	usd
CY2022	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	-1061000	usd
CY2021	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	307000	usd
CY2023	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6336000	usd
CY2022	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6250000	usd
CY2021	us-gaap	Other Noninterest Expense OtherNoninterestExpense	5379000	usd
CY2023	us-gaap	Noninterest Expense NoninterestExpense	83450000	usd
CY2022	us-gaap	Noninterest Expense NoninterestExpense	76948000	usd
CY2021	us-gaap	Noninterest Expense NoninterestExpense	79159000	usd
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	51760000	usd
CY2022	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	84859000	usd
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	97127000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14091000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	23740000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26473000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	37669000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	61119000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	70654000	usd
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.86
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.32
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.46
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.86
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.32
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.45
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	43560844	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	46234122	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	48416495	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	43638616	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	46438119	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	48754263	shares
CY2023	us-gaap	Net Income Loss NetIncomeLoss	37669000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	61119000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	70654000	usd
CY2023	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	22396000	usd
CY2022	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-69876000	usd
CY2021	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-13916000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-17000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	279000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	1495000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	22413000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-70155000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-15411000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	344000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-172000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	0	usd
CY2023	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	22069000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	-69983000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	-15411000	usd
CY2023	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	6269000	usd
CY2022	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-19558000	usd
CY2021	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-3895000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-5000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	79000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	419000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	94000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-48000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	0	usd
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	15889000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-50394000	usd
CY2023	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	53558000	usd
CY2022	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	10725000	usd
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	59557000	usd
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	753981000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	70654000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-11097000	usd
CY2021	us-gaap	Amortization Of Esop Award AmortizationOfESOPAward	2649000	usd
CY2021	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	994000	usd
CY2021	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	0	usd
CY2021	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	0	usd
CY2021	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	3409000	usd
CY2021	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.50
CY2021	us-gaap	Dividends Common Stock DividendsCommonStock	24299000	usd
CY2021	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	15.91
CY2021	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	53321000	usd
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	739883000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	61119000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-50394000	usd
CY2022	us-gaap	Amortization Of Esop Award AmortizationOfESOPAward	2375000	usd
CY2022	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1753000	usd
CY2022	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	0	usd
CY2022	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	0	usd
CY2022	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	1662000	usd
CY2022	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.52
CY2022	us-gaap	Dividends Common Stock DividendsCommonStock	24127000	usd
CY2022	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	14.72
CY2022	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	30881000	usd
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	701390000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	37669000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	15889000	usd
CY2023	us-gaap	Amortization Of Esop Award AmortizationOfESOPAward	1982000	usd
CY2023	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	2383000	usd
CY2023	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	0	usd
CY2023	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	0	usd
CY2023	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	100000	usd
CY2023	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.52
CY2023	us-gaap	Dividends Common Stock DividendsCommonStock	22795000	usd
CY2023	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	12307	shares
CY2023	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	304000	usd
CY2023	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	304000	usd
CY2023	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	11.99
CY2023	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	36869000	usd
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	699445000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	37669000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	61119000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	70654000	usd
CY2022	us-gaap	Payments To Acquire Finance Receivables PaymentsToAcquireFinanceReceivables	10183000	usd
CY2021	us-gaap	Payments To Acquire Finance Receivables PaymentsToAcquireFinanceReceivables	0	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	1353000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	4482000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-6184000	usd
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	4365000	usd
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	4128000	usd
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	3643000	usd
CY2023	us-gaap	Depreciation Nonproduction DepreciationNonproduction	3678000	usd
CY2022	us-gaap	Depreciation Nonproduction DepreciationNonproduction	3645000	usd
CY2021	us-gaap	Depreciation Nonproduction DepreciationNonproduction	3889000	usd
CY2023	nfbk	Amortization Of Premiums And Deferred Loan Costs AmortizationOfPremiumsAndDeferredLoanCosts	6651000	usd
CY2022	nfbk	Amortization Of Premiums And Deferred Loan Costs AmortizationOfPremiumsAndDeferredLoanCosts	9306000	usd
CY2021	nfbk	Amortization Of Premiums And Deferred Loan Costs AmortizationOfPremiumsAndDeferredLoanCosts	2587000	usd
CY2023	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	223000	usd
CY2022	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	112000	usd
CY2021	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	0	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	124000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	174000	usd
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	200000	usd
CY2023	us-gaap	Operating Lease Right Of Use Asset Amortization Expense OperatingLeaseRightOfUseAssetAmortizationExpense	4731000	usd
CY2022	us-gaap	Operating Lease Right Of Use Asset Amortization Expense OperatingLeaseRightOfUseAssetAmortizationExpense	4626000	usd
CY2021	us-gaap	Operating Lease Right Of Use Asset Amortization Expense OperatingLeaseRightOfUseAssetAmortizationExpense	4395000	usd
CY2023	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3631000	usd
CY2022	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3414000	usd
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	4103000	usd
CY2023	us-gaap	Gain Loss On Sale Of Notes Receivable GainLossOnSaleOfNotesReceivable	134000	usd
CY2022	us-gaap	Gain Loss On Sale Of Notes Receivable GainLossOnSaleOfNotesReceivable	453000	usd
CY2021	us-gaap	Gain Loss On Sale Of Notes Receivable GainLossOnSaleOfNotesReceivable	1401000	usd
CY2023	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	1583000	usd
CY2022	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	3544000	usd
CY2021	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	0	usd
CY2023	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	1449000	usd
CY2022	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	3364000	usd
CY2021	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	0	usd
CY2023	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	-17000	usd
CY2022	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	279000	usd
CY2021	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	1495000	usd
CY2023	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1721000	usd
CY2022	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-2206000	usd
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1703000	usd
CY2023	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-7000	usd
CY2022	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	17000	usd
CY2021	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	0	usd
CY2023	us-gaap	Increase Decrease In Trading Securities IncreaseDecreaseInTradingSecurities	77000	usd
CY2022	us-gaap	Increase Decrease In Trading Securities IncreaseDecreaseInTradingSecurities	-504000	usd
CY2021	us-gaap	Increase Decrease In Trading Securities IncreaseDecreaseInTradingSecurities	-533000	usd
CY2023	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	1065000	usd
CY2022	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	2924000	usd
CY2021	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-118000	usd
CY2023	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	8947000	usd
CY2022	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	3673000	usd
CY2021	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	14531000	usd
CY2023	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	-2919000	usd
CY2022	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	625000	usd
CY2021	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	-3159000	usd
CY2023	us-gaap	Increase Decrease In Other Accounts Payable And Accrued Liabilities IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities	674000	usd
CY2022	us-gaap	Increase Decrease In Other Accounts Payable And Accrued Liabilities IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities	4234000	usd
CY2021	us-gaap	Increase Decrease In Other Accounts Payable And Accrued Liabilities IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities	4998000	usd
CY2023	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	46970000	usd
CY2022	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	83331000	usd
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	64759000	usd
CY2023	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	-35875000	usd
CY2022	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	430849000	usd
CY2021	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	105455000	usd
CY2023	us-gaap	Payments To Acquire Finance Receivables PaymentsToAcquireFinanceReceivables	3781000	usd
CY2023	us-gaap	Proceeds From Sale Of Finance Receivables ProceedsFromSaleOfFinanceReceivables	0	usd
CY2022	us-gaap	Proceeds From Sale Of Finance Receivables ProceedsFromSaleOfFinanceReceivables	2796000	usd
CY2021	us-gaap	Proceeds From Sale Of Finance Receivables ProceedsFromSaleOfFinanceReceivables	151559000	usd
CY2023	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	45318000	usd
CY2022	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	44564000	usd
CY2021	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	220000	usd
CY2023	nfbk	Redemptions Of Federal Home Loan Bank Stock RedemptionsOfFederalHomeLoanBankStock	36033000	usd
CY2022	nfbk	Redemptions Of Federal Home Loan Bank Stock RedemptionsOfFederalHomeLoanBankStock	36518000	usd
CY2021	nfbk	Redemptions Of Federal Home Loan Bank Stock RedemptionsOfFederalHomeLoanBankStock	6525000	usd
CY2023	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	73544000	usd
CY2022	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	168973000	usd
CY2021	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	746967000	usd
CY2023	us-gaap	Payments To Acquire Marketable Securities PaymentsToAcquireMarketableSecurities	186000	usd
CY2022	us-gaap	Payments To Acquire Marketable Securities PaymentsToAcquireMarketableSecurities	5046000	usd
CY2021	us-gaap	Payments To Acquire Marketable Securities PaymentsToAcquireMarketableSecurities	5089000	usd
CY2023	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	247455000	usd
CY2022	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	305027000	usd
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	454414000	usd
CY2023	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	877000	usd
CY2022	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	720000	usd
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	1879000	usd
CY2023	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	usd
CY2022	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	6237000	usd
CY2021	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	usd
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	usd
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	41479000	usd
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	328966000	usd
CY2023	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	usd
CY2022	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1526000	usd
CY2021	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1021000	usd
CY2023	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	63000	usd
CY2022	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	125000	usd
CY2021	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	0	usd
CY2023	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	3605000	usd
CY2022	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	2552000	usd
CY2021	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1638000	usd
CY2023	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	193869000	usd
CY2022	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-280213000	usd
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	84995000	usd
CY2023	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-271784000	usd
CY2022	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-19115000	usd
CY2021	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	92783000	usd
CY2023	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	22795000	usd
CY2022	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	24127000	usd
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	24299000	usd
CY2023	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	100000	usd
CY2022	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1662000	usd
CY2021	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	3409000	usd
CY2023	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	37173000	usd
CY2022	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	30881000	usd
CY2021	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	53321000	usd
CY2023	us-gaap	Increase Decrease In Advance Payments By Borrowers For Taxes And Insurance IncreaseDecreaseInAdvancePaymentsByBorrowersForTaxesAndInsurance	-893000	usd
CY2022	us-gaap	Increase Decrease In Advance Payments By Borrowers For Taxes And Insurance IncreaseDecreaseInAdvancePaymentsByBorrowersForTaxesAndInsurance	1086000	usd
CY2021	us-gaap	Increase Decrease In Advance Payments By Borrowers For Taxes And Insurance IncreaseDecreaseInAdvancePaymentsByBorrowersForTaxesAndInsurance	5232000	usd
CY2023	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	0	usd
CY2022	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	60884000	usd
CY2021	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	0	usd
CY2023	nfbk	Proceeds From Securities Sold Under Agreements To Repurchase ProceedsFromSecuritiesSoldUnderAgreementsToRepurchase	743553000	usd
CY2022	nfbk	Proceeds From Securities Sold Under Agreements To Repurchase ProceedsFromSecuritiesSoldUnderAgreementsToRepurchase	282104000	usd
CY2021	nfbk	Proceeds From Securities Sold Under Agreements To Repurchase ProceedsFromSecuritiesSoldUnderAgreementsToRepurchase	0	usd
CY2023	nfbk	Payments For Securities Sold Under Agreements To Repurchase PaymentsForSecuritiesSoldUnderAgreementsToRepurchase	468140000	usd
CY2022	nfbk	Payments For Securities Sold Under Agreements To Repurchase PaymentsForSecuritiesSoldUnderAgreementsToRepurchase	120000000	usd
CY2021	nfbk	Payments For Securities Sold Under Agreements To Repurchase PaymentsForSecuritiesSoldUnderAgreementsToRepurchase	170034000	usd
CY2023	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-57132000	usd
CY2022	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	151613000	usd
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-146230000	usd
CY2023	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	183707000	usd
CY2022	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-45269000	usd
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	3524000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	45799000	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	91068000	usd
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	87544000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	229506000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	45799000	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	91068000	usd
CY2023	us-gaap	Interest Paid Net InterestPaidNet	80400000	usd
CY2022	us-gaap	Interest Paid Net InterestPaidNet	19282000	usd
CY2021	us-gaap	Interest Paid Net InterestPaidNet	17451000	usd
CY2023	us-gaap	Income Taxes Paid IncomeTaxesPaid	14704000	usd
CY2022	us-gaap	Income Taxes Paid IncomeTaxesPaid	22094000	usd
CY2021	us-gaap	Income Taxes Paid IncomeTaxesPaid	28476000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff After Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery	6435000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff After Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery	838000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff After Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery	2803000	usd
CY2023	us-gaap	Financing Receivable Reclassification To Held For Sale FinancingReceivableReclassificationToHeldForSale	0	usd
CY2022	us-gaap	Financing Receivable Reclassification To Held For Sale FinancingReceivableReclassificationToHeldForSale	2523000	usd
CY2021	us-gaap	Financing Receivable Reclassification To Held For Sale FinancingReceivableReclassificationToHeldForSale	131883000	usd
CY2023	us-gaap	Transfer Of Loans Held For Sale To Portfolio Loans1 TransferOfLoansHeldForSaleToPortfolioLoans1	0	usd
CY2022	us-gaap	Transfer Of Loans Held For Sale To Portfolio Loans1 TransferOfLoansHeldForSaleToPortfolioLoans1	0	usd
CY2021	us-gaap	Transfer Of Loans Held For Sale To Portfolio Loans1 TransferOfLoansHeldForSaleToPortfolioLoans1	1612000	usd
CY2023	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	0	usd
CY2022	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	0	usd
CY2021	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	100000	usd
CY2023	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	645000	usd
CY2022	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4983000	usd
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	1596000	usd
CY2023	nfbk	Activity Based Investment Component As Percentage Of Outstanding Advances ActivityBasedInvestmentComponentAsPercentageOfOutstandingAdvances	0.045
CY2023Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	2400000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	2800000	usd
CY2023Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	12800000	usd
CY2022Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	11700000	usd
CY2023Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	12800000	usd
CY2022Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	11700000	usd
CY2023	nfbk	Threshold Of Membership Investment Component Percentage ThresholdOfMembershipInvestmentComponentPercentage	0.00125
CY2023	nfbk	Threshold Of Membership Investment Component ThresholdOfMembershipInvestmentComponent	1000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	41000000	usd
CY2023	nfbk	Employee Stock Ownership Plan Esop Debt Structure Direct Loan Repayment Period EmployeeStockOwnershipPlanEsopDebtStructureDirectLoanRepaymentPeriod	P30Y
CY2023	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	77772	shares
CY2022	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	203997	shares
CY2021	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	337768	shares
CY2023Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss	840485000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	60000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	45081000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Excluding Accrued Interest DebtSecuritiesAvailableForSaleExcludingAccruedInterest	795464000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss	1019607000	usd
CY2022Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	3000	usd
CY2022Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	67437000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Excluding Accrued Interest DebtSecuritiesAvailableForSaleExcludingAccruedInterest	952173000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Restricted DebtSecuritiesAvailableForSaleRestricted	272900000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Restricted DebtSecuritiesAvailableForSaleRestricted	591700000	usd
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	usd
CY2023	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	22000	usd
CY2023	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	39000	usd
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	41500000	usd
CY2022	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	279000	usd
CY2022	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	usd
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	329000000	usd
CY2021	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1500000	usd
CY2021	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	usd
CY2023	us-gaap	Debt Securities Trading Realized Gain Loss DebtSecuritiesTradingRealizedGainLoss	1700000	usd
CY2022	us-gaap	Debt Securities Trading Realized Gain Loss DebtSecuritiesTradingRealizedGainLoss	-2200000	usd
CY2021	us-gaap	Debt Securities Trading Realized Gain Loss DebtSecuritiesTradingRealizedGainLoss	1700000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	9000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	21199000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	430053000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	46238000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	504194000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	67437000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	934247000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	2400000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	2800000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	9866000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	107000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	387000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	9586000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	10760000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	90000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	461000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	10389000	usd
CY2023	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest Sale DebtSecuritiesHeldToMaturityExcludingAccruedInterestSale	0	usd
CY2022	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest Sale DebtSecuritiesHeldToMaturityExcludingAccruedInterestSale	0	usd
CY2021	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest Sale DebtSecuritiesHeldToMaturityExcludingAccruedInterestSale	0	usd
CY2023Q4	us-gaap	Held To Maturity Securities Restricted HeldToMaturitySecuritiesRestricted	9700000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Restricted HeldToMaturitySecuritiesRestricted	2000000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	0	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	0	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	387000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	6661000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	387000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	6661000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	461000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	7433000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	0	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	0	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	461000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	7433000	usd
CY2023Q4	nfbk	Debt Securities Held To Maturity Unrealized Loss Position Greater Than Twelve Months Number Of Positions DebtSecuritiesHeldToMaturityUnrealizedLossPositionGreaterThanTwelveMonthsNumberOfPositions	9	security
CY2023Q4	us-gaap	Debt Securities Held To Maturity Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAccruedInterestAfterAllowanceForCreditLoss	36000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAccruedInterestAfterAllowanceForCreditLoss	39000	usd
CY2023Q4	us-gaap	Equity Securities Fv Ni And Without Readily Determinable Fair Value EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue	10600000	usd
CY2022Q4	us-gaap	Equity Securities Fv Ni And Without Readily Determinable Fair Value EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue	10400000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	4203654000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	4243693000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	37535000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	42617000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest After Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss	4166119000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest After Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss	4201076000	usd
CY2023Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	0	usd
CY2022Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	0	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual FinancingReceivableExcludingAccruedInterestNonaccrual	10100000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual FinancingReceivableExcludingAccruedInterestNonaccrual	9800000	usd
CY2023	nfbk	Delinquent Status Classification Criteria Days Minimum DelinquentStatusClassificationCriteriaDaysMinimum	P90D
CY2023	nfbk	Delinquent Status Classification Criteria Days Minimum DelinquentStatusClassificationCriteriaDaysMinimum	P90D
CY2023Q4	nfbk	Principal Balance Threshold For Non Accrual Status PrincipalBalanceThresholdForNonAccrualStatus	500000	usd
CY2023Q4	nfbk	Loans Deemed To Be Impaired Non Accrual Amount LoansDeemedToBeImpairedNonAccrualAmount	6000000	usd
CY2022Q4	nfbk	Loans Deemed To Be Impaired Non Accrual Amount LoansDeemedToBeImpairedNonAccrualAmount	5200000	usd
CY2023Q4	nfbk	Principal Balance Threshold For Non Accrual Status PrincipalBalanceThresholdForNonAccrualStatus	500000	usd
CY2023Q4	nfbk	Loans On Non Accrual Status With Principal Balances Below Threshold Definition Of An Impaired Loan LoansOnNonAccrualStatusWithPrincipalBalancesBelowThresholdDefinitionOfAnImpairedLoan	4100000	usd
CY2022Q4	nfbk	Loans On Non Accrual Status With Principal Balances Below Threshold Definition Of An Impaired Loan LoansOnNonAccrualStatusWithPrincipalBalancesBelowThresholdDefinitionOfAnImpairedLoan	4600000	usd
CY2022	nfbk	Delinquent Status Classification Criteria Days Minimum DelinquentStatusClassificationCriteriaDaysMinimum	P90D
CY2023	nfbk	Delinquent Status Classification Criteria Days Minimum DelinquentStatusClassificationCriteriaDaysMinimum	P90D
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest90 Days Or More Past Due Still Accruing FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing	1300000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest90 Days Or More Past Due Still Accruing FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing	425000	usd
CY2022	nfbk	Delinquent Status Classification Criteria Days Minimum DelinquentStatusClassificationCriteriaDaysMinimum	P90D
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual FinancingReceivableExcludingAccruedInterestNonaccrual	10115000	usd
CY2023Q4	nfbk	Financing Receivable Excluding Accrued Interest Nonaccrual Unpaid Principal Balance FinancingReceivableExcludingAccruedInterestNonaccrualUnpaidPrincipalBalance	15197000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual No Allowance FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance	6042000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual FinancingReceivableExcludingAccruedInterestNonaccrual	9813000	usd
CY2022Q4	nfbk	Financing Receivable Excluding Accrued Interest Nonaccrual Unpaid Principal Balance FinancingReceivableExcludingAccruedInterestNonaccrualUnpaidPrincipalBalance	10851000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual No Allowance FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance	5186000	usd
CY2023	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	581000	usd
CY2022	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	343000	usd
CY2023Q4	nfbk	Financing Receivable Impaired Secured By Collateral FinancingReceivableImpairedSecuredByCollateral	7900000	usd
CY2022Q4	nfbk	Financing Receivable Impaired Secured By Collateral FinancingReceivableImpairedSecuredByCollateral	7400000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Modified Period FinancingReceivableExcludingAccruedInterestModifiedPeriod	16034000	usd
CY2023	us-gaap	Financing Receivable Modification To Total Financing Receivables Excluding Accrued Interest Percent FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent
CY2023	us-gaap	Financing Receivable Modified Weighted Average Interest Rate Decrease From Modification FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification	0.0375
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Modified Period FinancingReceivableExcludingAccruedInterestModifiedPeriod	16034000	usd
CY2022	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	0	contract
CY2022Q4	nfbk	Trouble Debt Restructuring Amount TroubleDebtRestructuringAmount	7000000	usd
CY2022	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	contract
CY2023Q4	nfbk	Financing Receivable Threshold Individually Evaluated For Impairment FinancingReceivableThresholdIndividuallyEvaluatedForImpairment	500000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	45200	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	38200	usd
CY2022Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	791000	usd
CY2021Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	1852000	usd
CY2023	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	-555000	usd
CY2022	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	-1061000	usd
CY2023Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	236000	usd
CY2022Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	791000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	42617000	usd
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	38973000	usd
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	37607000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	1353000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	4482000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-6184000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	145000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	487000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	278000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	6580000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	1325000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	3081000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	42617000	usd
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	38973000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	42617000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	45000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	34405000	usd
CY2023Q4	nfbk	Financing Receivable Allowance For Credit Losses Pcd Loans Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesPCDLoansEvaluatedForImpairment	3085000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	4203654000	usd
CY2023Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	9324000	usd
CY2023Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	4184147000	usd
CY2023Q4	nfbk	Financing Receivables Pcd Loans Evaluated For Impairment FinancingReceivablesPCDLoansEvaluatedForImpairment	9899000	usd
CY2023Q4	nfbk	Financing Receivable Not Evaluated For Impairment FinancingReceivableNotEvaluatedForImpairment	284000	usd
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	38973000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	1325000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	487000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	4482000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	42617000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	38000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	38696000	usd
CY2022Q4	nfbk	Financing Receivable Allowance For Credit Losses Pcd Loans Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesPCDLoansEvaluatedForImpairment	3883000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	4243693000	usd
CY2022Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	8939000	usd
CY2023Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1277866000	usd
CY2022Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	4218109000	usd
CY2022Q4	nfbk	Financing Receivables Pcd Loans Evaluated For Impairment FinancingReceivablesPCDLoansEvaluatedForImpairment	11502000	usd
CY2022Q4	nfbk	Financing Receivable Not Evaluated For Impairment FinancingReceivableNotEvaluatedForImpairment	5143000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	37500000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	42600000	usd
CY2023Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	86481000	usd
CY2022Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	82875000	usd
CY2023Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	61710000	usd
CY2022Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	58031000	usd
CY2023Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	24771000	usd
CY2022Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	24844000	usd
CY2023	us-gaap	Depreciation Depreciation	3700000	usd
CY2022	us-gaap	Depreciation Depreciation	3600000	usd
CY2021	us-gaap	Depreciation Depreciation	3900000	usd
CY2022	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	0	usd
CY2021	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	0	usd
CY2023	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	0	usd
CY2023Q4	us-gaap	Deposits Negotiable Order Of Withdrawal Now DepositsNegotiableOrderOfWithdrawalNOW	1231943000	usd
CY2023Q4	us-gaap	Weighted Average Rate Domestic Deposit Notice Of Withdrawal WeightedAverageRateDomesticDepositNoticeOfWithdrawal	0.0206
CY2022Q4	us-gaap	Deposits Negotiable Order Of Withdrawal Now DepositsNegotiableOrderOfWithdrawalNOW	1132290000	usd
CY2022Q4	us-gaap	Weighted Average Rate Domestic Deposit Notice Of Withdrawal WeightedAverageRateDomesticDepositNoticeOfWithdrawal	0.0051
CY2023Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	694903000	usd
CY2022Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	852660000	usd
CY2023Q4	nfbk	Deposits Transactions DepositsTransactions	1926846000	usd
CY2023Q4	nfbk	Weighted Average Rate Domestic Deposit Transaction WeightedAverageRateDomesticDepositTransaction	0.0132
CY2022Q4	nfbk	Deposits Transactions DepositsTransactions	1984950000	usd
CY2022Q4	nfbk	Weighted Average Rate Domestic Deposit Transaction WeightedAverageRateDomesticDepositTransaction	0.0029
CY2023Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	302122000	usd
CY2023Q4	us-gaap	Weighted Average Rate Domestic Deposit Money Market WeightedAverageRateDomesticDepositMoneyMarket	0.0176
CY2022Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	508067000	usd
CY2022Q4	us-gaap	Weighted Average Rate Domestic Deposit Money Market WeightedAverageRateDomesticDepositMoneyMarket	0.0047
CY2023Q4	us-gaap	Interest Bearing Domestic Deposit Brokered InterestBearingDomesticDepositBrokered	50000000	usd
CY2023Q4	us-gaap	Weighted Average Rate Domestic Deposit Savings WeightedAverageRateDomesticDepositSavings	0.0196
CY2023Q4	us-gaap	Weighted Average Rate Domestic Deposit Brokered WeightedAverageRateDomesticDepositBrokered	0.0530
CY2022Q4	us-gaap	Interest Bearing Domestic Deposit Brokered InterestBearingDomesticDepositBrokered	0	usd
CY2023Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	925744000	usd
CY2023Q4	nfbk	Weighted Average Interest Rate Of Time Deposits Interest Bearing Deposit Liabilities WeightedAverageInterestRateOfTimeDepositsInterestBearingDepositLiabilities	0.0185
CY2022Q4	us-gaap	Interest Bearing Deposit Liabilities InterestBearingDepositLiabilities	917180000	usd
CY2022Q4	nfbk	Weighted Average Interest Rate Of Time Deposits Interest Bearing Deposit Liabilities WeightedAverageInterestRateOfTimeDepositsInterestBearingDepositLiabilities	0.0014
CY2022Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1425247000	usd
CY2022Q4	us-gaap	Weighted Average Rate Domestic Deposit Savings WeightedAverageRateDomesticDepositSavings	0.0026
CY2023Q4	us-gaap	Time Deposits Less Than100000 TimeDepositsLessThan100000	257691000	usd
CY2023Q4	nfbk	Weighted Average Interest Rateof Time Deposits Less Than100000 WeightedAverageInterestRateofTimeDepositsLessThan100000	0.0393
CY2022Q4	us-gaap	Time Deposits Less Than100000 TimeDepositsLessThan100000	525944000	usd
CY2022Q4	nfbk	Weighted Average Interest Rateof Time Deposits Less Than100000 WeightedAverageInterestRateofTimeDepositsLessThan100000	0.0306
CY2023Q4	us-gaap	Time Deposits100000 Or More TimeDeposits100000OrMore	416032000	usd
CY2023Q4	us-gaap	Weighted Average Interest Rate Of Time Deposits100000 Or More WeightedAverageInterestRateOfTimeDeposits100000OrMore	0.0428
CY2022Q4	us-gaap	Time Deposits100000 Or More TimeDeposits100000OrMore	214078000	usd
CY2022Q4	us-gaap	Weighted Average Interest Rate Of Time Deposits100000 Or More WeightedAverageInterestRateOfTimeDeposits100000OrMore	0.0117
CY2023Q4	us-gaap	Time Deposits TimeDeposits	673723000	usd
CY2023Q4	us-gaap	Weighted Average Rate Domestic Deposit Time Deposits WeightedAverageRateDomesticDepositTimeDeposits	0.0415
CY2022Q4	us-gaap	Time Deposits TimeDeposits	740022000	usd
CY2022Q4	us-gaap	Weighted Average Rate Domestic Deposit Time Deposits WeightedAverageRateDomesticDepositTimeDeposits	0.0251
CY2023Q4	us-gaap	Deposits Deposits	3878435000	usd
CY2023Q4	us-gaap	Weighted Average Rate Domestic Deposit WeightedAverageRateDomesticDeposit	0.0202
CY2022Q4	us-gaap	Deposits Deposits	4150219000	usd
CY2022Q4	us-gaap	Weighted Average Rate Domestic Deposit WeightedAverageRateDomesticDeposit	0.0068
CY2023Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	635793000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	16719000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	5119000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	6628000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	9464000	usd
CY2023Q4	us-gaap	Time Deposits TimeDeposits	673723000	usd
CY2023Q4	nfbk	Certificates Of Deposit Exceed Fdic Insurance Limit CertificatesOfDepositExceedFDICInsuranceLimit	98200000	usd
CY2022Q4	nfbk	Certificates Of Deposit Exceed Fdic Insurance Limit CertificatesOfDepositExceedFDICInsuranceLimit	56800000	usd
CY2023	nfbk	Interest Expense Domestic Deposit Liabilities Transaction InterestExpenseDomesticDepositLiabilitiesTransaction	16553000	usd
CY2022	nfbk	Interest Expense Domestic Deposit Liabilities Transaction InterestExpenseDomesticDepositLiabilitiesTransaction	1759000	usd
CY2021	nfbk	Interest Expense Domestic Deposit Liabilities Transaction InterestExpenseDomesticDepositLiabilitiesTransaction	805000	usd
CY2023	nfbk	Interest Expense Domestic Deposit Liabilities Savings And Money Market InterestExpenseDomesticDepositLiabilitiesSavingsAndMoneyMarket	13855000	usd
CY2022	nfbk	Interest Expense Domestic Deposit Liabilities Savings And Money Market InterestExpenseDomesticDepositLiabilitiesSavingsAndMoneyMarket	1851000	usd
CY2021	nfbk	Interest Expense Domestic Deposit Liabilities Savings And Money Market InterestExpenseDomesticDepositLiabilitiesSavingsAndMoneyMarket	2226000	usd
CY2023	us-gaap	Interest Expense Domestic Deposit Liabilities Certificates Of Deposit InterestExpenseDomesticDepositLiabilitiesCertificatesOfDeposit	18345000	usd
CY2022	us-gaap	Interest Expense Domestic Deposit Liabilities Certificates Of Deposit InterestExpenseDomesticDepositLiabilitiesCertificatesOfDeposit	6679000	usd
CY2021	us-gaap	Interest Expense Domestic Deposit Liabilities Certificates Of Deposit InterestExpenseDomesticDepositLiabilitiesCertificatesOfDeposit	3176000	usd
CY2023	us-gaap	Interest Expense Deposits InterestExpenseDeposits	48753000	usd
CY2022	us-gaap	Interest Expense Deposits InterestExpenseDeposits	10289000	usd
CY2021	us-gaap	Interest Expense Deposits InterestExpenseDeposits	6207000	usd
CY2023Q4	nfbk	Repurchase Agreement Included In Overnight Accounts RepurchaseAgreementIncludedInOvernightAccounts	25000000	usd
CY2022Q4	nfbk	Repurchase Agreement Included In Overnight Accounts RepurchaseAgreementIncludedInOvernightAccounts	25000000	usd
CY2023Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	733553000	usd
CY2022Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	547000000	usd
CY2023Q4	nfbk	Long Term Debt Bank Term Funding Program Borrowings LongTermDebtBankTermFundingProgramBorrowings	94500000	usd
CY2022Q4	nfbk	Long Term Debt Bank Term Funding Program Borrowings LongTermDebtBankTermFundingProgramBorrowings	0	usd
CY2023Q4	nfbk	Long Term Debt Floating Rate Advances And Other Interest Bearing Liabilities LongTermDebtFloatingRateAdvancesAndOtherInterestBearingLiabilities	6219000	usd
CY2022Q4	nfbk	Long Term Debt Floating Rate Advances And Other Interest Bearing Liabilities LongTermDebtFloatingRateAdvancesAndOtherInterestBearingLiabilities	11859000	usd
CY2023Q4	us-gaap	Long Term Debt LongTermDebt	859272000	usd
CY2022Q4	us-gaap	Long Term Debt LongTermDebt	583859000	usd
CY2022Q4	nfbk	Overnight Line Of Credit OvernightLineOfCredit	177000000	usd
CY2023Q4	nfbk	Additional Funding Federal Home Loan Bank Advances Long Term AdditionalFundingFederalHomeLoanBankAdvancesLongTerm	1420000000	usd
CY2023Q4	nfbk	Unencumbered Securities UnencumberedSecurities	493700000	usd
CY2023Q4	nfbk	Multifamily Loans Held As Collateral By Federal Home Loan Bank MultifamilyLoansHeldAsCollateralByFederalHomeLoanBank	931000000	usd
CY2022Q2	us-gaap	Subordinated Debt SubordinatedDebt	62000000	usd
CY2023	us-gaap	Subordinated Borrowing Interest Rate SubordinatedBorrowingInterestRate	0.0500
CY2022Q2	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	1100000	usd
CY2023Q4	us-gaap	Subordinated Debt SubordinatedDebt	61200000	usd
CY2022Q4	us-gaap	Subordinated Debt SubordinatedDebt	61000000	usd
CY2023Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	781000	usd
CY2022Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	1000000	usd
CY2023Q4	us-gaap	Accumulated Amortization Deferred Finance Costs AccumulatedAmortizationDeferredFinanceCosts	223000	usd
CY2022Q4	us-gaap	Accumulated Amortization Deferred Finance Costs AccumulatedAmortizationDeferredFinanceCosts	112000	usd
CY2023	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	7438000	usd
CY2022	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	15784000	usd
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	15313000	usd
CY2023	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	1880000	usd
CY2022	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-233000	usd
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	3107000	usd
CY2023	us-gaap	Federal Income Tax Expense Benefit Continuing Operations FederalIncomeTaxExpenseBenefitContinuingOperations	9318000	usd
CY2022	us-gaap	Federal Income Tax Expense Benefit Continuing Operations FederalIncomeTaxExpenseBenefitContinuingOperations	15551000	usd
CY2021	us-gaap	Federal Income Tax Expense Benefit Continuing Operations FederalIncomeTaxExpenseBenefitContinuingOperations	18420000	usd
CY2023	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	3734000	usd
CY2022	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	8581000	usd
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	8001000	usd
CY2023	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	1039000	usd
CY2022	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-392000	usd
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	52000	usd
CY2023	us-gaap	State And Local Income Tax Expense Benefit Continuing Operations StateAndLocalIncomeTaxExpenseBenefitContinuingOperations	4773000	usd
CY2022	us-gaap	State And Local Income Tax Expense Benefit Continuing Operations StateAndLocalIncomeTaxExpenseBenefitContinuingOperations	8189000	usd
CY2021	us-gaap	State And Local Income Tax Expense Benefit Continuing Operations StateAndLocalIncomeTaxExpenseBenefitContinuingOperations	8053000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14091000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	23740000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26473000	usd
CY2023	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	10869000	usd
CY2022	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	17820000	usd
CY2021	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	20397000	usd
CY2023	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2022	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2021	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2023	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	3770000	usd
CY2022	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	6469000	usd
CY2021	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	6362000	usd
CY2023	nfbk	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsuranceAmount	762000	usd
CY2022	nfbk	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsuranceAmount	717000	usd
CY2021	nfbk	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsuranceAmount	862000	usd
CY2023	nfbk	Income Tax Rate Reconciliation Deduction Employee Stock Ownership Plan Fair Market Value Adjustment Amount IncomeTaxRateReconciliationDeductionEmployeeStockOwnershipPlanFairMarketValueAdjustmentAmount	-6000	usd
CY2022	nfbk	Income Tax Rate Reconciliation Deduction Employee Stock Ownership Plan Fair Market Value Adjustment Amount IncomeTaxRateReconciliationDeductionEmployeeStockOwnershipPlanFairMarketValueAdjustmentAmount	69000	usd
CY2021	nfbk	Income Tax Rate Reconciliation Deduction Employee Stock Ownership Plan Fair Market Value Adjustment Amount IncomeTaxRateReconciliationDeductionEmployeeStockOwnershipPlanFairMarketValueAdjustmentAmount	102000	usd
CY2023	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	0	usd
CY2022	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	0	usd
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	6000	usd
CY2023	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	220000	usd
CY2022	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	99000	usd
CY2021	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	468000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14091000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	23740000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26473000	usd
CY2023Q4	nfbk	Deferred Tax Assets Allowance For Credit Losses DeferredTaxAssetsAllowanceForCreditLosses	10703000	usd
CY2022Q4	nfbk	Deferred Tax Assets Allowance For Credit Losses DeferredTaxAssetsAllowanceForCreditLosses	12202000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	2814000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	2958000	usd
CY2023Q4	nfbk	Deferred Tax Assets Accrued Salaries And Benefits And Other DeferredTaxAssetsAccruedSalariesAndBenefitsAndOther	463000	usd
CY2022Q4	nfbk	Deferred Tax Assets Accrued Salaries And Benefits And Other DeferredTaxAssetsAccruedSalariesAndBenefitsAndOther	1610000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	283000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	313000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	2113000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	2091000	usd
CY2023Q4	nfbk	Deferred Tax Assets Net Actuarial Loss On Defined Benefit Post Retirement Benefit Plans DeferredTaxAssetsNetActuarialLossOnDefinedBenefitPostRetirementBenefitPlans	9000	usd
CY2022Q4	nfbk	Deferred Tax Assets Net Actuarial Loss On Defined Benefit Post Retirement Benefit Plans DeferredTaxAssetsNetActuarialLossOnDefinedBenefitPostRetirementBenefitPlans	0	usd
CY2023Q4	nfbk	Deferred Tax Assets Straight Line Rent Adjustments DeferredTaxAssetsStraightLineRentAdjustments	1461000	usd
CY2022Q4	nfbk	Deferred Tax Assets Straight Line Rent Adjustments DeferredTaxAssetsStraightLineRentAdjustments	1608000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Asset Retirement Obligations DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations	48000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Asset Retirement Obligations DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations	47000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Returns And Allowances DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReturnsAndAllowances	694000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Returns And Allowances DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReturnsAndAllowances	681000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	69000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	231000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	631000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	633000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	381000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	323000	usd
CY2023Q4	nfbk	Deferred Tax Assets Depreciation DeferredTaxAssetsDepreciation	3791000	usd
CY2022Q4	nfbk	Deferred Tax Assets Depreciation DeferredTaxAssetsDepreciation	3552000	usd
CY2023Q4	nfbk	Deferred Tax Assets Related To Fair Value Adjustments On Business Acquisitions DeferredTaxAssetsRelatedToFairValueAdjustmentsOnBusinessAcquisitions	755000	usd
CY2022Q4	nfbk	Deferred Tax Assets Related To Fair Value Adjustments On Business Acquisitions DeferredTaxAssetsRelatedToFairValueAdjustmentsOnBusinessAcquisitions	1057000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	140000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	130000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Unrealized Losses On Availablefor Sale Securities Gross DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross	12601000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Unrealized Losses On Availablefor Sale Securities Gross DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross	18875000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	36956000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	46311000	usd
CY2023Q4	nfbk	Deferred Tax Liabilities Unrealized Actuarial Gains On Post Retirement Benefits DeferredTaxLiabilitiesUnrealizedActuarialGainsOnPostRetirementBenefits	0	usd
CY2022Q4	nfbk	Deferred Tax Liabilities Unrealized Actuarial Gains On Post Retirement Benefits DeferredTaxLiabilitiesUnrealizedActuarialGainsOnPostRetirementBenefits	65000	usd
CY2023Q4	nfbk	Deferred Tax Liabilities Adjustment Of Investment Securities DeferredTaxLiabilitiesAdjustmentOfInvestmentSecurities	151000	usd
CY2022Q4	nfbk	Deferred Tax Liabilities Adjustment Of Investment Securities DeferredTaxLiabilitiesAdjustmentOfInvestmentSecurities	280000	usd
CY2023Q4	nfbk	Deferred Tax Liabilities Adjustment Of Deposit Liabilities DeferredTaxLiabilitiesAdjustmentOfDepositLiabilities	31000	usd
CY2022Q4	nfbk	Deferred Tax Liabilities Adjustment Of Deposit Liabilities DeferredTaxLiabilitiesAdjustmentOfDepositLiabilities	32000	usd
CY2023Q4	nfbk	Deferred Tax Liability Deferred Loan Fees DeferredTaxLiabilityDeferredLoanFees	2481000	usd
CY2022Q4	nfbk	Deferred Tax Liability Deferred Loan Fees DeferredTaxLiabilityDeferredLoanFees	2553000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	51000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	20000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	2714000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	2950000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	34242000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	43361000	usd
CY2023	nfbk	Amount Of Bad Debts Reserved For In Current Year AmountOfBadDebtsReservedForInCurrentYear	5900000	usd
CY2022	nfbk	Amount Of Bad Debts Reserved For In Current Year AmountOfBadDebtsReservedForInCurrentYear	5900000	usd
CY2023Q4	nfbk	Federal Tax Bad Debt Deferred Tax Liability FederalTaxBadDebtDeferredTaxLiability	1700000	usd
CY2022Q4	nfbk	Federal Tax Bad Debt Deferred Tax Liability FederalTaxBadDebtDeferredTaxLiability	1700000	usd
CY2022Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	87000	usd
CY2021Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	141000	usd
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	157000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	135000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	31000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	125000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	347000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	23000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	109000	usd
CY2023Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	299000	usd
CY2022Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	87000	usd
CY2021Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	141000	usd
CY2023	nfbk	Defined Contribution Plan Requisite Service Period DefinedContributionPlanRequisiteServicePeriod	P30D
CY2023	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	0.25
CY2023	nfbk	Percentage Contribution From Employees First Base Compensation PercentageContributionFromEmployeesFirstBaseCompensation	0.06
CY2023	nfbk	Defined Contribution Plan Vesting Period DefinedContributionPlanVestingPeriod	P3Y
CY2023	nfbk	Defined Contribution Plan Periodof Participationto Trigger Increasein Employee Contribution Percentage DefinedContributionPlanPeriodofParticipationtoTriggerIncreaseinEmployeeContributionPercentage	P3Y
CY2023	nfbk	Percentage Contribution From Employees First Base Compensation PercentageContributionFromEmployeesFirstBaseCompensation	0.06
CY2023	nfbk	Defined Contribution Plan Requisite Service Periodto Become Fully Vested DefinedContributionPlanRequisiteServicePeriodtoBecomeFullyVested	P5Y
CY2023	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	629000	usd
CY2022	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	553000	usd
CY2021	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	515000	usd
CY2023	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	1300000	usd
CY2022	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	1700000	usd
CY2021	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	1900000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Amortization Of Gain Loss Next Fiscal Year DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear	-9000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Amortization Of Prior Service Cost Credit Next Fiscal Year DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear	-19000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Ultimate Health Care Cost Trend Rate1 DefinedBenefitPlanUltimateHealthCareCostTrendRate1	0.0825
CY2023	nfbk	Defined Benefit Plan Ultimate Health Care Cost Trend Rate Reduction DefinedBenefitPlanUltimateHealthCareCostTrendRateReduction	0.0050
CY2023Q4	us-gaap	Defined Benefit Plan Health Care Cost Trend Rate Assumed Next Fiscal Year DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear	0.0475
CY2023	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	106000	usd
CY2022	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	81000	usd
CY2021	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	99000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	105000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	102000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	100000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	96000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	92000	usd
CY2023Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	395000	usd
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2023	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	2400000	usd
CY2022	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	1800000	usd
CY2021	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	994000	usd
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	1769979	shares
CY2021Q4	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageGrantDateFairValue	4.02
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	13.95
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P2Y11M12D
CY2022	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	187153	shares
CY2022	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageGrantDateFairValue	3.92
CY2022	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	13.23
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	1582826	shares
CY2022Q4	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageGrantDateFairValue	4.03
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	14.04
CY2022	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P2Y3D
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	30920	shares
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Options Forfeited Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue	3.97
CY2023	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	13.79
CY2023	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	7600	shares
CY2023	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageGrantDateFairValue	3.91
CY2023	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	13.13
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	1544306	shares
CY2023Q4	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageGrantDateFairValue	4.03
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	14.05
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P1Y3D
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	1544306	shares
CY2023Q4	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageGrantDateFairValue	4.03
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	14.05
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P1Y3D
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod	27842	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	222844	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	13.21
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	181908	shares
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	15.78
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	62836	shares
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	12.87
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	20415	shares
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	14.34
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	321501	shares
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	14.66
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	192249	shares
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	14.37
CY2023	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Incremental ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIncremental	10353	shares
CY2023	nfbk	Share Based Compensation Arrangement By Share Based Payment Award Equity Instrument Other Than Options Incremental Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentOtherThanOptionsIncrementalWeightedAverageGrantDateFairValue	0
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	124586	shares
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	13.96
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	37791	shares
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CY2023Q4	nfbk	Commitments To Extend Credit Allowance For Estimated Losses CommitmentsToExtendCreditAllowanceForEstimatedLosses	236000	usd
CY2022Q4	nfbk	Commitments To Extend Credit Allowance For Estimated Losses CommitmentsToExtendCreditAllowanceForEstimatedLosses	791000	usd
CY2023	nfbk	Agreement Term AgreementTerm	P3Y
CY2023	nfbk	Agreement Term AgreementTerm	P3Y
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CY2023Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.080
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CY2023Q4	us-gaap	Tier One Leverage Capital Required To Be Well Capitalized To Average Assets TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets	0.050
CY2023Q4	nfbk	Tier One Common Capital Requiredtobe Well Capitalizedto Risk Weighted Assets TierOneCommonCapitalRequiredtobeWellCapitalizedtoRiskWeightedAssets	0.065
CY2023Q4	us-gaap	Tier One Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	0.080
CY2023Q4	us-gaap	Capital Required To Be Well Capitalized To Risk Weighted Assets CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	0.100
CY2023Q4	nfbk	Tier One Common Capital Requiredfor Capital Adequacyto Risk Weighted Assets TierOneCommonCapitalRequiredforCapitalAdequacytoRiskWeightedAssets	0.045
CY2023Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.06
CY2023Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.08
CY2023Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.04
CY2023Q4	nfbk	Tier One Risk Based Capital Requiredfor Capital Adequacyto Risk Weighted Assets Higher Risk Weight TierOneRiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetsHigherRiskWeight	0.025
CY2023Q4	nfbk	Banking Regulation Community Bank Leverage Ratio Actual BankingRegulationCommunityBankLeverageRatioActual	690721000	usd
CY2023Q4	nfbk	Banking Regulation Community Bank Leverage Ratio Capital Ratio Actual BankingRegulationCommunityBankLeverageRatioCapitalRatioActual	0.1258
CY2023Q4	nfbk	Banking Regulation Community Bank Leverage Ratio Capital Adequacy Minimum Amount BankingRegulationCommunityBankLeverageRatioCapitalAdequacyMinimumAmount	494043000	usd
CY2023Q4	nfbk	Banking Regulation Community Bank Leverage Ratio Capital Adequacy Minimum BankingRegulationCommunityBankLeverageRatioCapitalAdequacyMinimum	0.0900
CY2023Q4	nfbk	Banking Regulation Community Bank Leverage Ratio Well Capitalized Minimum Amount BankingRegulationCommunityBankLeverageRatioWellCapitalizedMinimumAmount	494043000	usd
CY2023Q4	nfbk	Banking Regulation Community Bank Leverage Ratio Well Capitalized Minimum BankingRegulationCommunityBankLeverageRatioWellCapitalizedMinimum	0.0900
CY2022Q4	nfbk	Tier One Common Equity TierOneCommonEquity	708430000	usd
CY2022Q4	nfbk	Tier One Common Capitalto Risk Weighted Assets TierOneCommonCapitaltoRiskWeightedAssets	0.1265
CY2022Q4	nfbk	Tier One Common Equity Requiredfor Capital Adequacy TierOneCommonEquityRequiredforCapitalAdequacy	503977000	usd
CY2022Q4	nfbk	Tier One Common Capital Requiredfor Capital Adequacyto Risk Weighted Assets TierOneCommonCapitalRequiredforCapitalAdequacytoRiskWeightedAssets	0.0900
CY2022Q4	nfbk	Tier One Common Equity Requiredtobe Well Capitalized TierOneCommonEquityRequiredtobeWellCapitalized	503977000	usd
CY2022Q4	nfbk	Tier One Common Capital Requiredtobe Well Capitalizedto Risk Weighted Assets TierOneCommonCapitalRequiredtobeWellCapitalizedtoRiskWeightedAssets	0.0900
CY2023Q4	nfbk	Investment Owned At Net Asset Value InvestmentOwnedAtNetAssetValue	10300000	usd
CY2022Q4	nfbk	Investment Owned At Net Asset Value InvestmentOwnedAtNetAssetValue	10100000	usd
CY2023Q4	us-gaap	Loans Receivable Fair Value Disclosure LoansReceivableFairValueDisclosure	4277000	usd
CY2022Q4	us-gaap	Loans Receivable Fair Value Disclosure LoansReceivableFairValueDisclosure	4640000	usd
CY2023Q4	nfbk	Principal Amount Outstanding Of Impaired Loans Heldfor Investment And Heldfor Sale PrincipalAmountOutstandingOfImpairedLoansHeldforInvestmentAndHeldforSale	6000000	usd
CY2022Q4	nfbk	Principal Amount Outstanding Of Impaired Loans Heldfor Investment And Heldfor Sale PrincipalAmountOutstandingOfImpairedLoansHeldforInvestmentAndHeldforSale	6700000	usd
CY2023Q4	nfbk	Estimated Fair Value Of Impaired Loans Held For Investment EstimatedFairValueOfImpairedLoansHeldForInvestment	4300000	usd
CY2022Q4	nfbk	Estimated Fair Value Of Impaired Loans Held For Investment EstimatedFairValueOfImpairedLoansHeldForInvestment	4600000	usd
CY2023	us-gaap	Asset Impairment Charges AssetImpairmentCharges	7000	usd
CY2022	us-gaap	Asset Impairment Charges AssetImpairmentCharges	8000	usd
CY2023	nfbk	Impaired Financing Receivables Charge Off ImpairedFinancingReceivablesChargeOff	6400000	usd
CY2022	nfbk	Impaired Financing Receivables Charge Off ImpairedFinancingReceivablesChargeOff	838000	usd
CY2022Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	0	usd
CY2023Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	0	usd
CY2023Q4	nfbk	Investment Owned At Net Asset Value InvestmentOwnedAtNetAssetValue	10300000	usd
CY2022	nfbk	Derivative Asset Statement Of Financial Position Extensible Enumeration Not Disclosed Flag DerivativeAssetStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag	Derivative assets
CY2022	nfbk	Derivative Liability Statement Of Financial Position Extensible Enumeration Not Disclosed Flag DerivativeLiabilityStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag	Derivative liabilities
CY2022Q4	nfbk	Investment Owned At Net Asset Value InvestmentOwnedAtNetAssetValue	10100000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	37669000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	61119000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	70654000	usd
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	43560844	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	46234122	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	48416495	shares
CY2023	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	77772	shares
CY2022	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	203997	shares
CY2021	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	337768	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	43638616	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	46438119	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	48754263	shares
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.86
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.32
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.46
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.86
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.32
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.45
CY2023	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1542194	shares
CY2022	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	756765	shares
CY2021	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	323466	shares
CY2023Q2	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	10000000	usd
CY2023Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	7500000	usd
CY2021	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	0	shares
CY2022	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	0	shares
CY2021	us-gaap	Variable Lease Cost VariableLeaseCost	4092000	usd
CY2023	us-gaap	Lease Cost LeaseCost	9881000	usd
CY2022	us-gaap	Lease Cost LeaseCost	9627000	usd
CY2021	us-gaap	Lease Cost LeaseCost	9889000	usd
CY2023	us-gaap	Operating Lease Payments OperatingLeasePayments	6487000	usd
CY2023	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5479000	usd
CY2022	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5705000	usd
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5394000	usd
CY2023	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3631000	usd
CY2022	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3414000	usd
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	4103000	usd
CY2023	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	-17000	usd
CY2022	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	279000	usd
CY2021	us-gaap	Debt Securities Available For Sale Gain Loss DebtSecuritiesAvailableForSaleGainLoss	1495000	usd
CY2023	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1721000	usd
CY2022	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-2206000	usd
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	1703000	usd
CY2023	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	134000	usd
CY2022	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	453000	usd
CY2021	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1401000	usd
CY2023	us-gaap	Revenue Not From Contract With Customer Other RevenueNotFromContractWithCustomerOther	948000	usd
CY2022	us-gaap	Revenue Not From Contract With Customer Other RevenueNotFromContractWithCustomerOther	338000	usd
CY2021	us-gaap	Revenue Not From Contract With Customer Other RevenueNotFromContractWithCustomerOther	357000	usd
CY2023	us-gaap	Noninterest Income NoninterestIncome	11896000	usd
CY2022	us-gaap	Noninterest Income NoninterestIncome	7983000	usd
CY2021	us-gaap	Noninterest Income NoninterestIncome	14453000	usd
CY2023Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	30200000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	35200000	usd
CY2022Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	34300000	usd
CY2022Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	39800000	usd
CY2023	us-gaap	Operating Lease Cost OperatingLeaseCost	6037000	usd
CY2022	us-gaap	Operating Lease Cost OperatingLeaseCost	6006000	usd
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	5797000	usd
CY2023	us-gaap	Variable Lease Cost VariableLeaseCost	3844000	usd
CY2022	us-gaap	Variable Lease Cost VariableLeaseCost	3621000	usd
CY2022	us-gaap	Operating Lease Payments OperatingLeasePayments	6350000	usd
CY2021	us-gaap	Operating Lease Payments OperatingLeasePayments	6538000	usd
CY2023	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	645000	usd
CY2022	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4983000	usd
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	1596000	usd
CY2023Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P11Y1M2D
CY2022Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P11Y2M19D
CY2021Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P11Y10M2D
CY2023Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0360
CY2022Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0354
CY2021Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0355
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	6133000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	5792000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	5029000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	4068000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	3803000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	19343000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	44168000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	8963000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	35205000	usd
CY2023	us-gaap	Operating Lease Expense OperatingLeaseExpense	6000000	usd
CY2022	us-gaap	Operating Lease Expense OperatingLeaseExpense	6100000	usd
CY2021	us-gaap	Operating Lease Expense OperatingLeaseExpense	5900000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Lease Not Yet Commenced Term Of Contract1 LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1	P10Y
CY2023Q4	nfbk	Lessee Operating Lease Lease Not Yet Commenced Liability LesseeOperatingLeaseLeaseNotYetCommencedLiability	850000	usd
CY2023	nfbk	Lessee Operating Lease Term Of Intent To Exercise Options LesseeOperatingLeaseTermOfIntentToExerciseOptions	P5Y
CY2023Q4	us-gaap	Lessee Operating Lease Renewal Term LesseeOperatingLeaseRenewalTerm	P5Y
CY2023	nfbk	Operating Leases Fixed Rent Per Month OperatingLeasesFixedRentPerMonth	19657	usd
CY2023Q4	us-gaap	Lessee Operating Lease Term Of Contract LesseeOperatingLeaseTermOfContract	P5Y
CY2023	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	223000	usd
CY2022	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	112000	usd
CY2021	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	0	usd
CY2023Q4	ecd	Rule10b51 Arr Adopted Flag Rule10b51ArrAdoptedFlag	false
CY2023Q4	ecd	Non Rule10b51 Arr Adopted Flag NonRule10b51ArrAdoptedFlag	false
CY2023Q4	ecd	Non Rule10b51 Arr Trmntd Flag NonRule10b51ArrTrmntdFlag	false
CY2023Q4	ecd	Rule10b51 Arr Trmntd Flag Rule10b51ArrTrmntdFlag	false
CY2023	dei	Auditor Name AuditorName	Crowe, LLP
CY2023	dei	Auditor Location AuditorLocation	Livingston, New Jersey
CY2023	dei	Auditor Firm AuditorFirmId	173

Files In Submission

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$NFBK
Northfield Bancorp, Inc. Stock $nfbk

2024 Q1 Form 10-K Financial Statement

#000149322524000059 Filed on February 29, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NFBK Northfield Bancorp, Inc. Stock $nfbk

2024 Q1 Form 10-K Financial Statement

#000149322524000059 Filed on February 29, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NFBK
Northfield Bancorp, Inc. Stock $nfbk