Annual report pursuant to Section 13 and 15(d)

SEVERANCE ARRANGEMENTS (Details)

v2.4.1.9
SEVERANCE ARRANGEMENTS (Details) (USD $)
 3 Months Ended 12 Months Ended
Sep. 30, 2012
Dec. 31, 2012
Former President [Member]    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Period of postemployment health care coverage   18 months
Estimated expenses for bonus, vehicle and continuation coverage pursuant to COBRA $ 600,000us-gaap_PostemploymentBenefitsPeriodExpense
/ us-gaap_TitleOfIndividualAxis
= us-gaap_PresidentMember 		 
Former President [Member] | Restricted Stock [Member]    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Non-cash stock compensation costs 4,300,000nog_NonCashStockCompensationCosts
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_RestrictedStockMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_PresidentMember 		 
Chief Operating Officer [Member]    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Period of postemployment health care coverage   18 months
Base salary considered for severance benefits to be paid   325,000nog_BaseSalaryConsideredForSeveranceBenefitsToBePaid
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ChiefOperatingOfficerMember