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Changes in Standardized Measure of Discounted Future Net Cash Flows (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]    
Balance beginning of year $ 43,646,905 $ 25,304,892
Sales, net of production costs (5,394,198) (2,869,339)
Net change in pricing and production costs 2,870,156 11,287,884
Net change in future estimated development costs (1,001,445) (702,640)
Purchase of minerals in place 0 16,834,878
Extensions and discoveries 11,274,543 7,598,861
Sale of minerals in place 0 (5,322,346)
Sale of Rantoul Partners interest 0 (4,765,069)
Revisions (4,329,483) (3,147,460)
Accretion of discount 5,324,900 3,119,577
Change in income tax (3,518,817) (3,692,333)
Balance end of year $ 48,872,560 $ 43,646,905