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EARNINGS PER SHARE (Details) (USD $)
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12 Months Ended | ||
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Basic EPS [Abstract] | |||
| Net Income available to common shareholders | $ 163,745,945us-gaap_ProfitLoss | $ 53,067,036us-gaap_ProfitLoss | $ 72,284,624us-gaap_ProfitLoss |
| Shares-Basic (in shares) | 60,691,701us-gaap_WeightedAverageNumberOfSharesOutstandingBasic | 62,364,957us-gaap_WeightedAverageNumberOfSharesOutstandingBasic | 62,485,836us-gaap_WeightedAverageNumberOfSharesOutstandingBasic |
| Net Income per basic share (in dollars per share) | $ 2.70us-gaap_EarningsPerShareBasic | $ 0.85us-gaap_EarningsPerShareBasic | $ 1.16us-gaap_EarningsPerShareBasic |
| Diluted EPS [Abstract] | |||
| Dilutive effect of options (in shares) | 169,068us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements | 382,341us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements | 383,243us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements |
| Dilutive effect of options (in dollars per share) | $ (0.01)nog_DilutiveSecuritiesEffectOnBasicEarningsPerShare | $ 0nog_DilutiveSecuritiesEffectOnBasicEarningsPerShare | $ (0.01)nog_DilutiveSecuritiesEffectOnBasicEarningsPerShare |
| Net Income available to common shareholders, diluted | $ 163,745,945us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted | $ 53,067,036us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted | $ 72,284,624us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted |
| Weighted Average Common Shares Outstanding - Diluted (in shares) | 60,860,769us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding | 62,747,298us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding | 62,869,079us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding |
| Earnings Per Share - Diluted (in dollars per share) | $ 2.69us-gaap_EarningsPerShareDiluted | $ 0.85us-gaap_EarningsPerShareDiluted | $ 1.15us-gaap_EarningsPerShareDiluted |
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Shares excluded from EPS due to the anti-dilutive effect (in shares) | 15,590us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 7,330us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 18,348us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount |
| Restricted Stock [Member] | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Shares 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 |
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| X | ||||||||||
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- Definition
The per share amount resulting from the "as if" assumption that stock options or restrictive stock units were exercised for purposes of computing the dilutive effect of convertible securities. No definition available.
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| X | ||||||||||
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- Definition
Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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| X | ||||||||||
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- Definition
The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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| X | ||||||||||
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- Definition
Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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