Selected Quarterly Financial Data (Unaudited) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Line Items]
Impairment of proved properties and other	$ 0	$ 63,679	$ 0	$ 0	$ 0	$ 0	$ 0	$ 43,040		$ 63,679	$ 43,040	$ 590,174
MRD Merger expenses					$ 813	$ 33,791	$ 2,621	0	$ 37,200	$ 0	$ 37,225	$ 0
Oklahoma and Texas Properties
Selected Quarterly Financial Information [Line Items]
Impairment of proved properties and other		$ 63,700
Western Oklahoma Properties
Selected Quarterly Financial Information [Line Items]
Impairment of proved properties and other								$ 43,000