Supplemental Information on Natural Gas and Oil Exploration, Development and Production Activities (Unaudited) - Changes in Discounted Future Net Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revisions of previous estimates
Changes in prices and production costs	$ (6,560,107)	$ 2,959,488	$ 2,615,825
Revisions in quantities	(12,741)	667,763	445,667
Changes in future development and abandonment costs	104,585	(686,632)	(814,215)
Net change in income taxes	1,125,639	(1,075,867)	(706,531)
Accretion of discount	1,317,349	814,725	372,743
Purchases of reserves in place	0	0	6,173
Additions to proved reserves from extensions, discoveries and improved recovery	552,710	2,543,296	2,128,135
Natural gas, NGLs and oil sales, net of production costs	(881,883)	(1,547,580)	(1,237,970)
Actual development costs incurred during the period	676,520	851,188	1,202,618
Sales of reserves in place	(688,937)	(226,953)	(32,946)
Timing and other	(120,156)	(349,048)	(266,214)
Net change for the year	(4,487,021)	3,950,380	3,713,285
Beginning of year	11,115,594	7,165,214	3,451,929
End of year	$ 6,628,573	$ 11,115,594	$ 7,165,214