Annual report pursuant to Section 13 and 15(d)

SIGNIFICANT ACCOUNTING POLICIES (Details)

v2.4.1.9
SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)
12 Months Ended 3 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Cash and Cash Equivalents [Abstract]              
Threshold amount of FDIC coverage $ 250,000nog_ThresholdAmountOfFdicCoverage     $ 250,000nog_ThresholdAmountOfFdicCoverage      
Accounts Receivable [Abstract]              
Allowance for doubtful accounts 1,840,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent 1,050,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent   1,840,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent      
Provision for doubtful accounts 1,375,000us-gaap_ProvisionForDoubtfulAccounts 1,050,000us-gaap_ProvisionForDoubtfulAccounts 0us-gaap_ProvisionForDoubtfulAccounts        
Charged against the allowance for doubtful accounts 585,000us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs 0us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs          
Advance to Operators [Abstract]              
Period for advance payments to be applied against joint interest billings 90 days            
Property, Plant and Equipment [Line Items]              
Depreciation expense 315,405us-gaap_DepreciationAndAmortization 325,859us-gaap_DepreciationAndAmortization 409,888us-gaap_DepreciationAndAmortization        
Full Cost Method [Abstract]              
Capitalized Certain Payroll and Other Internal Costs 2,153,448nog_CapitalizedCertainPayrollAndOtherInternalCosts 3,295,427nog_CapitalizedCertainPayrollAndOtherInternalCosts 8,477,678nog_CapitalizedCertainPayrollAndOtherInternalCosts        
Capitalized Interest Cost 4,409,544us-gaap_InterestCostsCapitalized 5,976,981us-gaap_InterestCostsCapitalized 5,929,473us-gaap_InterestCostsCapitalized        
Total 6,562,992nog_TotalCapitalizedCostsOilAndGasProducingActivities 9,272,408nog_TotalCapitalizedCostsOilAndGasProducingActivities 14,407,151nog_TotalCapitalizedCostsOilAndGasProducingActivities        
Minimum percentage of proved reserves sold to be considered a significant alteration (in hundredths) 25.00%nog_PercentageOfProvedReservesSoldToBeConsideredSignificantAlteration            
Proceeds from sale of oil and gas properties 0nog_ProceedsFromSaleOfOilAndGasPropertyAndEquipmentUsedToReduceCapitalizedCostsOfCrudeOilAndNaturalGasProperties 0nog_ProceedsFromSaleOfOilAndGasPropertyAndEquipmentUsedToReduceCapitalizedCostsOfCrudeOilAndNaturalGasProperties 908,000nog_ProceedsFromSaleOfOilAndGasPropertyAndEquipmentUsedToReduceCapitalizedCostsOfCrudeOilAndNaturalGasProperties        
Capitalized costs related to expired leases subject to depletion 26,300,000nog_CapitalizedCostsRelatedToExpiredLeasesSubjectToDepletion 14,100,000nog_CapitalizedCostsRelatedToExpiredLeasesSubjectToDepletion 7,100,000nog_CapitalizedCostsRelatedToExpiredLeasesSubjectToDepletion        
Impairment costs related to expired leases subject to depletion 21,400,000nog_ImpairmentCostsRelatedToExpiredLeasesSubjectToDepletion 5,100,000nog_ImpairmentCostsRelatedToExpiredLeasesSubjectToDepletion 0nog_ImpairmentCostsRelatedToExpiredLeasesSubjectToDepletion        
Discount rate (in hundredths) 10.00%nog_CrudeOilAndNaturalGasPropertiesDiscountRate            
Debt Issuance Costs [Abstract]              
Amortization of debt issuance costs 2,776,024us-gaap_AmortizationOfFinancingCosts 2,625,240us-gaap_AmortizationOfFinancingCosts 1,527,194us-gaap_AmortizationOfFinancingCosts        
Rate of Senior notes (in hundredths) 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage   8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage      
Amortization of bond premium 1,486,726nog_AmortizationOfBondPremium 960,177nog_AmortizationOfBondPremium 0nog_AmortizationOfBondPremium        
Income Taxes [Abstract]              
Valuation allowance 0us-gaap_DeferredTaxAssetsValuationAllowance 0us-gaap_DeferredTaxAssetsValuationAllowance   0us-gaap_DeferredTaxAssetsValuationAllowance      
Net Income Per Common Share [Abstract]              
Weighted Average Common Shares Outstanding - Basic (in shares) 60,691,701us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 62,364,957us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 62,485,836us-gaap_WeightedAverageNumberOfSharesOutstandingBasic        
Plus: Potentially Dilutive Common Shares Including Stock Options and Restricted Stock (in shares) 169,068nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares 382,341nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares 383,243nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares        
Weighted Average Common Shares Outstanding - Diluted (in shares) 60,860,769us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 62,747,298us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 62,869,079us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding        
Restricted Stock Excluded From EPS Due To The Anti-Dilutive Effect (in shares) 15,590us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 7,330us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 18,348us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount        
Impairment [Abstract]              
Asset Impairment Charges 0us-gaap_AssetImpairmentCharges 0us-gaap_AssetImpairmentCharges 0us-gaap_AssetImpairmentCharges        
Stock Options [Member]              
Net Income Per Common Share [Abstract]              
Plus: Potentially Dilutive Common Shares Including Stock Options and Restricted Stock (in shares) 141,872nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
241,872nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
251,963nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
       
Exercise price (in dollars per share) $ 5.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
$ 5.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
$ 5.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
$ 5.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
     
Restricted Stock [Member]              
Net Income Per Common Share [Abstract]              
Plus: Potentially Dilutive Common Shares Including Stock Options and Restricted Stock (in shares) 538,499nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
592,565nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
777,437nog_IncrementalCommonSharesAttributableToStockOptionsAndWarrantsAndRestrictedShares
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
       
Restricted Stock Excluded From EPS Due To The Anti-Dilutive Effect (in shares) 15,590us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
7,330us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
         
Senior Unsecured Notes [Member]              
Debt Issuance Costs [Abstract]              
Capitalized costs in connection with debt $ 10,500,000nog_CapitalizedCostsInConnectionWithDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
    $ 10,500,000nog_CapitalizedCostsInConnectionWithDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
     
Rate of Senior notes (in hundredths) 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
    8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
     
NYMEX [Member]              
Defined Price Per Unit [Line Items]              
Defined price for each quarter       94.99nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_NewYorkMercantileExchangeMember
99.08nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_NewYorkMercantileExchangeMember
100.11nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_NewYorkMercantileExchangeMember
98.30nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_NewYorkMercantileExchangeMember
Henry Hub [Member]              
Defined Price Per Unit [Line Items]              
Defined price for each quarter       4.35nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_HenryHubMember
4.24nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_HenryHubMember
4.10nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_HenryHubMember
3.99nog_OilAndGasDefinedPricePerUnit
/ nog_TypeOfRegulatoryBodiesAxis
= nog_HenryHubMember
Minimum [Member]              
Property, Plant and Equipment [Line Items]              
Property and equipment, estimated useful lives 3 years            
Maximum [Member]              
Property, Plant and Equipment [Line Items]              
Property and equipment, estimated useful lives 7 years