Summary of Property and Equipment (Detail) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020 USD ($) $ / bbl	Jun. 30, 2020 USD ($)	Sep. 30, 2019 USD ($) $ / bbl	Sep. 30, 2020 USD ($) $ / bbl	Sep. 30, 2019 USD ($) $ / bbl	Dec. 31, 2019 USD ($)
Property, Plant and Equipment [Abstract]
Asset Impairment Charges	$ 235,989	$ 35,500	$ 0	$ 271,498	$ 0
Proved Oil and Gas Property, Full Cost Method	1,509,097			1,509,097		$ 1,409,219
Unproved Oil and Gas Property, Full Cost Method	52,910			52,910		53,200
Oil and Gas Property, Full Cost Method, Gross	1,562,007			1,562,007		1,462,419
Total properties and equipment	1,589,502			1,589,502		1,488,334
Other property and equipment	27,495			27,495		25,915
Accumulated depreciation, depletion and amortization	(754,002)			(754,002)		(367,909)
Property and equipment, net (successful efforts method)	835,500			835,500		1,120,425
Interest Costs Capitalized				2,100	3,200
Unproved Oil and Gas Property excluded	52,900			52,900		$ 53,200
Undeveloped Leasehold Costs Transferred				4,500	200
Capitalized Costs, Proved Properties	$ 1,300		$ 3,200	$ 1,300	$ 3,200
Amortization Expense Per Physical Unit of Production | $ / bbl	16.63		17.47	16.63	17.47