Assets and Liabilities Held for Sale - Additional Information (Detail)	Apr. 03, 2015 USD ($) a	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Summary Of Assets And Liabilities Held For Sale [Line Items]
Total assets held for sale		$ 14,164,597	$ 14,301,375
Marcellus Shale Wells [Member]
Summary Of Assets And Liabilities Held For Sale [Line Items]
Acres of Land Sold | a	5,159
Expects to receive approximately from sale of certain interests	$ 47,000,000
Number of wells	12
Marcellus Shale Wells [Member] | Royalty Interests [Member]
Summary Of Assets And Liabilities Held For Sale [Line Items]
Expects to receive approximately from sale of certain interests	$ 71,300,000
Wetzel County West Virginia [Member]
Summary Of Assets And Liabilities Held For Sale [Line Items]
Total assets held for sale		$ 14,164,597	$ 14,301,375