Natural Gas Producing Activities (Unaudited) - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / bbl $ / Dekatherm Bcfe	Dec. 31, 2018 USD ($) Bcfe	Dec. 31, 2017 USD ($) Bcfe
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Impairment and expiration of leases | $	$ 556,424	$ 279,708	$ 7,552
Unproved properties | $	$ 3,322,014	$ 4,166,048	$ 5,016,299
Engineer experience (in years)	19 years
Percentage of total net natural gas, NGL and oil proved reserves reviewed	100.00%
Percentage of proved developed reserves covered in the audit	94.00%
Percentage of audit coverage of remaining properties	6.00%
Transfers (in Bcfe)	2,646	2,722	987
Period increase (decrease) (in Bcfe)	2,068	4,739	2,225
Production (in Bcfe)	1,508	1,495	908
Inclusion in drilling plan (in Bcfe)	116	3,538	1,032
Increased reserves (in Bcfe)		148	477
Removal of locations, economic and lack of development (in Bcfe)	4,508	1,273	3,522
Change in economic life (in Bcfe)			278
Sale of mineral in place (in Bcfe)		1,749
Acquisitions (in Bcfe)			3,330
Acquisitions, developed (in Bcfe)			6,060
Removal of locations not expected to develop within 5 years (in Bcfe)			3,074
Discount rate to compute standard measure of future cash flow (as a percent)	10.00%
Discounted future net cash flows relating to proved oil and gas reserves, change in price of natural gas sensitivity (in usd per dth) | $ / Dekatherm	0.10
Discounted future net cash flows relating to proved oil and gas reserves, change in price of oil sensitivity (in usd per bbl) | $ / bbl	10
Discounted future net cash flows relating to proved oil and gas reserves, change in price of natural gas liquids (in usd per bbl) | $ / bbl	10
Change in discounted future cash flows for assumed natural gas price change | $	$ 809,000
Change in discounted future cash flows for assumed oil price change | $	24,000
Change in discounted future cash flows for assumed natural gas liquids price change | $	$ 163,000
Ohio, Pennsylvania, and West Virginia Marcellus
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Increased reserves (in Bcfe)	1,796	315	300
Ohio, Pennsylvania, and West Virginia Marcellus Acres
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Increased reserves (in Bcfe)	156	886	893