Natural Gas Producing Activities (Unaudited) - Summary of Changes in the Standardized Measure of Discounted Net Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Roll Forward]
Net sales and transfers of natural gas and oil produced	$ (1,884,877)	$ (2,802,742)	$ (1,305,186)
Net changes in prices, production and development costs	(3,502,434)	2,949,606	2,236,183
Extensions, discoveries and improved recovery, net of related costs	870,504	1,616,653	1,269,712
Development costs incurred	1,002,389	1,630,506	712,635
Net purchase of minerals in place	0	0	5,357,921
Net sale of minerals in place	0	(849,162)	(284)
Revisions of previous quantity estimates	(2,080,040)	(811,576)	(297,437)
Accretion of discount	900,004	834,026	115,437
Net change in income taxes	1,444,368	(289,549)	(1,477,603)
Timing and other	130,861	332,202	1,401,802
Net (decrease) increase	(3,119,225)	2,609,964	8,013,180
Balance at January 1	11,611,898	9,001,934	988,754
Balance at December 31	$ 8,492,673	$ 11,611,898	$ 9,001,934