Annual report pursuant to Section 13 and 15(d)

DERIVATIVE INSTRUMENTS AND PRICE RISK MANAGEMENT (Details)

v2.4.1.9
DERIVATIVE INSTRUMENTS AND PRICE RISK MANAGEMENT (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]      
Volumes (Bpl) 4,900,000invest_DerivativeNonmonetaryNotionalAmount    
Weighted Average Price (in dollar per barrel) 89.53us-gaap_DerivativeSwapTypeAverageFixedPrice    
Notional volume barrels per month (in barrels) 90,000nog_DerivativeNotionalVolumeExercisablePerMonth    
Increase in derivative contracts (in barrels) 90,000nog_IncreaseInDerivativeNotionalVolumePerMonth    
Average price per barrel (in dollars per barrel) 91.00nog_DerivativeNotionalVolumeAveragePricePerMonth    
Oil Swap 1 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 360,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap1Member
   
Fixed Price (in dollars per barrel) 89.15us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap1Member
   
Oil Swap 1 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 1 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 2 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 60,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap2Member
   
Fixed Price (in dollars per barrel) 90.50us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap2Member
   
Oil Swap 2 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 2 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 3 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap3Member
   
Fixed Price (in dollars per barrel) 88.55us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap3Member
   
Oil Swap 3 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 3 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 4 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap4Member
   
Fixed Price (in dollars per barrel) 88.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap4Member
   
Oil Swap 4 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 4 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 5 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 60,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap5Member
   
Fixed Price (in dollars per barrel) 90.75us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap5Member
   
Oil Swap 5 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 5 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 6 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 60,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap6Member
   
Fixed Price (in dollars per barrel) 90.25us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap6Member
   
Oil Swap 6 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 6 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 7 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 90,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap7Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap7Member
   
Oil Swap 7 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 7 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 8 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 90,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap8Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap8Member
   
Oil Swap 8 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 8 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2015    
Oil Swap 9 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 720,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap9Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap9Member
   
Oil Swap 9 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 9 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015    
Oil Swap 10 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 360,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap10Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap10Member
   
Oil Swap 10 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 10 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015    
Oil Swap 11 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 360,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap11Member
   
Fixed Price (in dollars per barrel) 89.02us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap11Member
   
Oil Swap 11 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 11 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015    
Oil Swap 12 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap12Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap12Member
   
Oil Swap 12 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 12 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015    
Oil Swap 13 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap13Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap13Member
   
Oil Swap 13 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2015    
Oil Swap 13 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015    
Oil Swap 14 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap14Member
[1]    
Fixed Price (in dollars per barrel) 90.75us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap14Member
[1]    
Oil Swap 14 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jul. 01, 2015 [1]    
Oil Swap 14 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015 [1]    
Oil Swap 15 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap15Member
[1]    
Fixed Price (in dollars per barrel) 91.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap15Member
[1]    
Oil Swap 15 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jul. 01, 2015 [1]    
Oil Swap 15 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015 [1]    
Oil Swap 16 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap16Member
[1]    
Fixed Price (in dollars per barrel) 91.25us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap16Member
[1]    
Oil Swap 16 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jul. 01, 2015 [1]    
Oil Swap 16 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Dec. 31, 2015 [1]    
Oil Swap 17 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 360,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap17Member
   
Fixed Price (in dollars per barrel) 89.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap17Member
   
Oil Swap 17 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jul. 01, 2015    
Oil Swap 17 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2016    
Oil Swap 18 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 360,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap18Member
   
Fixed Price (in dollars per barrel) 90.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap18Member
   
Oil Swap 18 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jul. 01, 2015    
Oil Swap 18 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2016    
Oil Swap 19 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 360,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap19Member
   
Fixed Price (in dollars per barrel) 91.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap19Member
   
Oil Swap 19 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jul. 01, 2015    
Oil Swap 19 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2016    
Oil Swap 20 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 180,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap20Member
   
Fixed Price (in dollars per barrel) 90.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap20Member
   
Oil Swap 20 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2016    
Oil Swap 20 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2016    
Oil Swap 21 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 90,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap21Member
   
Fixed Price (in dollars per barrel) 90.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap21Member
   
Oil Swap 21 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2016    
Oil Swap 21 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2016    
Oil Swap 22 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Oil (in barrels) 90,000us-gaap_DerivativeNonmonetaryNotionalAmountVolume
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap22Member
   
Fixed Price (in dollars per barrel) 90.00us-gaap_DerivativeSwapTypeFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OilSwap22Member
   
Oil Swap 22 [Member] | Minimum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jan. 01, 2016    
Oil Swap 22 [Member] | Maximum [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Settlement period Jun. 30, 2016    
Open Commodity Swap 1 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Volumes (Bpl) 3,960,000invest_DerivativeNonmonetaryNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OpenCommoditySwap1Member
   
Weighted Average Price (in dollar per barrel) 89.43us-gaap_DerivativeSwapTypeAverageFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OpenCommoditySwap1Member
   
Open Commodity Swap 2 [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Volumes (Bpl) 900,000invest_DerivativeNonmonetaryNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OpenCommoditySwap2Member
   
Weighted Average Price (in dollar per barrel) 90.00us-gaap_DerivativeSwapTypeAverageFixedPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= nog_OpenCommoditySwap2Member
   
Not Designated as Hedging Instrument [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Realized gain (loss) on price risk derivatives not designated as hedges $ 7.9us-gaap_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstruments
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
$ 12.2us-gaap_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstruments
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
$ 0.4us-gaap_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstruments
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
Unrealized gain (loss) on price risk derivatives not designated as hedges $ 171.3nog_UnrealizedGainLossOnPriceRiskDerivativesNotDesignatedAsHedges
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
$ (21.3)nog_UnrealizedGainLossOnPriceRiskDerivativesNotDesignatedAsHedges
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
$ 15.1nog_UnrealizedGainLossOnPriceRiskDerivativesNotDesignatedAsHedges
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
[1] The Company has entered into crude oil derivative contracts that give counterparties the option to extend certain current derivative contracts for an additional six-month period. Options covering a notional volume of 90,000 barrels per month are exercisable on or about December 31, 2015. If the counterparties exercise all such options, the notional volume of the Company's existing crude oil derivative contracts will increase by 90,000 barrels per month at an average price of $91.00 per barrel for each month during the period January 1, 2016 through June 30, 2016.