Natural Gas Producing Activities (Unaudited) - Costs Incurred Relating to Natural Gas, NGL, and Oil Production Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Capitalized costs
Proved properties	$ 17,994,820	$ 17,648,731	$ 18,920,855
Unproved properties	3,322,014	4,166,048	5,016,299
Total capitalized costs	21,316,834	21,814,779	23,937,154
Less: Accumulated depreciation and depletion	5,402,515	4,666,212	5,121,646
Net capitalized costs	15,914,319	17,148,567	18,815,508
Property acquisition:
Proved properties	40,316	77,099	5,251,711
Unproved properties	154,128	198,854	3,310,995
Exploration	7,223	1,708	15,505
Development	$ 1,560,346	2,443,980	1,357,165
2017 Acquisitions | Marcellus Acres
Property acquisition:
Unproved properties			2,625,100
Proved properties, wells		5,200	2,530,400
Proved properties, leases			1,192,000
2017 Acquisitions | Utica Acres
Property acquisition:
Unproved properties			500
Proved properties, wells		$ 9,200	1,228,600
Proved properties, leases			$ 300