Quarterly report pursuant to Section 13 or 15(d)

COMMON AND PREFERRED STOCK (Details)

v2.4.1.9
COMMON AND PREFERRED STOCK (Details) (USD $)
3 Months Ended 12 Months Ended
Mar. 31, 2015
Class
Mar. 31, 2014
Dec. 31, 2014
COMMON AND PREFERRED STOCK [Abstract]      
Total shares of preferred and common stock authorized for issuance (in shares) 100,000,000nog_StockSharesAuthorized    
Number of classes of shares 2nog_NumberOfClassesOfShares    
Common stock, shares authorized (in shares) 95,000,000us-gaap_CommonStockSharesAuthorized   95,000,000us-gaap_CommonStockSharesAuthorized
Common stock, par value (in dollars per share) $ 0.001us-gaap_CommonStockParOrStatedValuePerShare   $ 0.001us-gaap_CommonStockParOrStatedValuePerShare
Preferred stock, shares authorized (in shares) 5,000,000us-gaap_PreferredStockSharesAuthorized   5,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, par value (in dollars per share) $ 0.001us-gaap_PreferredStockParOrStatedValuePerShare   $ 0.001us-gaap_PreferredStockParOrStatedValuePerShare
Changes in number of common stock shares [Roll forward]      
Beginning Balance (in shares) 61,066,712us-gaap_CommonStockSharesOutstanding 61,858,199us-gaap_CommonStockSharesOutstanding 61,858,199us-gaap_CommonStockSharesOutstanding
Stock Options Exercised (in shares) 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised   100,000us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Restricted Stock Grants (Note 6) (in shares) 497,854us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross   299,416us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross
Stock Repurchased (in shares) 0us-gaap_StockRepurchasedAndRetiredDuringPeriodShares (1,018,837)us-gaap_StockRepurchasedAndRetiredDuringPeriodShares (1,153,885)us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Other Surrenders (in shares) (11,257)us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited   (79,461)us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited
Other (in shares) 0us-gaap_StockIssuedDuringPeriodSharesOther   42,443us-gaap_StockIssuedDuringPeriodSharesOther
Ending Balance (in shares) 61,553,309us-gaap_CommonStockSharesOutstanding   61,066,712us-gaap_CommonStockSharesOutstanding
Stock Activity [Abstract]      
Common stock surrendered by certain employees to cover tax obligations (in shares) 11,257us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation    
Fair value of common stock surrendered by certain employees to cover tax obligations $ 76,379us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardForfeitures    
Stock Repurchase Program [Abstract]      
Stock repurchase program, amount approved 150,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1    
Treasury stock, repurchased and retired 13,700,000us-gaap_TreasuryStockRetiredCostMethodAmount    
Stock repurchase (in shares) 0us-gaap_StockRepurchasedAndRetiredDuringPeriodShares 1,018,837us-gaap_StockRepurchasedAndRetiredDuringPeriodShares 1,153,885us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Performance Stock [Member]      
Performance Stock [Abstract]      
Vesting Period 3 years    
Performance Stock [Member] | Minimum [Member]      
Performance Stock [Abstract]      
Participant's earning percentage (in hundredths) 0.00%nog_ParticipantsEarningPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
Performance Stock [Member] | Maximum [Member]      
Performance Stock [Abstract]      
Participant's earning percentage (in hundredths) 150.00%nog_ParticipantsEarningPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Maximum dollar amount of performance shares issuable $ 3,300,000nog_MaximumDollarAmountOfPerformanceSharesIssuable
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember