Properties and Equipment (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) Wells Rate	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) Wells	Dec. 31, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Document Period End Date	Mar. 31, 2021
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves	$ 0		$ (20,389)
Proved Natural Gas and Crude Oil Properties	7,650,594		7,523,639
Unproved Natural Gas and Crude Oil Properties	350,993		350,677
Total Natural Gas and Crude Oil Properties	8,001,587		7,874,316
Equipment and other	64,900		65,027
Land and Buildings	17,665		24,299
Construction in Progress	519,931		523,550
Properties and equipment, at cost	8,604,083		8,487,192
Accumulated DD&A	(3,771,285)		(3,627,993)
Property, Plant and Equipment, Net	4,832,798		4,859,199
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves	1,219		11,770
Capitalized Exploratory Well Costs	$ 8,678		$ 7,459	$ 16,078
Wells to be completed | Wells	2		2
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	$ 7,500		$ 7,500
Impairment Measurement Input | Rate	17000000.00%
Results of Operations, Impairment of Oil and Gas Properties	$ 0	$ 881,100
Delaware Basin Proved Property Impairment		753,000
Delaware Basin Unproved Property Impairment		$ 127,300