Supplemental Information on Oil and Gas Producing Activities (Unaudited) - Changes in standardized measure of discounted future net cash flow (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) $ / Mcfe	Dec. 31, 2020 USD ($) $ / Mcfe	Dec. 31, 2019 USD ($) $ / Mcfe
Reserve Quantities [Line Items]
12-month weighted average price (in dollars per Mcfe | $ / Mcfe	4.21	2.15	2.87
Changes in Standardized Measure of Discounted Future Net Cash Flow
Sales of oil and gas, net of productions costs	$ (2,917)	$ (347)	$ (1,116)
Net changes in prices and production costs	14,099	(5,455)	(6,729)
Development costs incurred during the period	454	704	758
Net changes in future development costs	(117)	249	(92)
Extensions, discoveries and other additions	504	31	782
Divestitures	(125)	(174)
Revisions of previous quantity estimates	2,543	(379)	(1,011)
Accretion of discount	121	607	1,259
Net change in income taxes	(3,115)	598	1,513
Changes in timing and other	776	(93)	(373)
Net decrease	12,223	(4,259)	(5,009)
Beginning of year	1,210	5,469	10,478
End of year	13,433	1,210	5,469
Increased production costs			3,300
Increased future development costs			$ 185
VIE, Martica
Changes in Standardized Measure of Discounted Future Net Cash Flow
Beginning of year	359
End of year	$ 501	$ 359