STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) (USD $)	6 Months Ended
Jun. 30, 2012
COMPREHENSIVE INCOME, NET OF TAX
Reclassification of Derivative Instruments Included in Income, Tax	$ 39,000

Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

No definition available.

Name:	nog_ReclassificationAdjustmentsForUnrealizedGainsOrLossesOnSaleOfSecuritiesAfterTax
Namespace Prefix:	nog_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration