Acquisitions and Dispositions - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended		1 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2013 Surface Acreage in North Texas	Sep. 30, 2014 Miscellaneous Proved Property	Sep. 30, 2013 Drilling Company	Sep. 30, 2013 Unproved Leases	Jun. 30, 2013 Delaware and Permian Basin	Sep. 30, 2013 Miscellaneous Proved and Unproved Properties	Sep. 30, 2014 EQT Corporation	Sep. 30, 2014 Nora Gathering, LLC	Sep. 30, 2014 Conger Exchange Transaction	Sep. 30, 2014 Conger Exchange Transaction	Apr. 30, 2014 Conger Exchange Transaction	Apr. 30, 2014 Conger Exchange Transaction EQT Corporation	Sep. 30, 2014 Conger Exchange Transaction EQT Corporation
Significant Acquisitions And Disposals [Line Items]
Cash proceeds from sale of assets											$ 145,000,000					$ 145,000,000
Sale and exchange transaction, closing date																	Jun. 16, 2014
Gain (loss) on sale of assets	167,000	6,008,000	281,878,000	89,129,000	253,000	1,700,000		1,700,000	83,300,000	4,100,000						275,200,000
Selling expenses for property sale									4,200,000								5,000,000
Carrying amount of assets prior to exchange															271,800,000
Percentage of ownership interest, acquired												50.00%
Percentage of ownership interest with Company												50.00%
Gain on sale of assets														10,000,000
Trade receivables relating to acquisition													5,500,000	5,500,000
Recognized revenue from sale of property interests acquired													18,400,000
Net operating income													14,600,000
Proceeds from sale of oil and gas					5,300,000	2,100,000		2,600,000	275,000,000	26,000,000
Proceeds from sale of business							7,000,000
Gain (Loss) on sale of business							$ 4,400,000