Acquisitions and Dispositions - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			6 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2014	Jun. 30, 2015	Jun. 16, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets		$ (681)		$ 167			$ 2,053	$ 281,878
Conger Exchange Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets								285,200
Cash proceeds from sale of assets	$ 145,000								$ 145,000
Net operating income prior to disposition			$ 14,600			$ 21,900
Sale and exchange transaction, closing date							Jun. 16, 2014
Selling expenses for property sale								5,000
Recognized revenue from sale of property interests acquire			$ 18,400
Miscellaneous Proved, Unproved Properties and Surface Acreage
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from sale of oil and gas		524			$ 14,300			2,100
(Loss) gain on the sale of assets		$ (681)			2,700			$ 1,700
West Texas Properties
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from sale of oil and gas					$ 10,500