Income Taxes - Components of Deferred Tax Assets & Liabilities (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Liabilities
Property, plant and equipment and investments	$ (1,712)	$ (847)
Other	(38)	(45)
Total Deferred Tax Liabilities	(1,750)	(892)
Deferred Tax Assets
Net operating loss carryforwards	4,323	5,037
Tax credit carryforwards	89	135
Property, plant and equipment and investments	258	55
Accrued compensation, deferred credits and other liabilities	71	196
Asset retirement obligations	258	252
Other	277	325
Total Deferred Tax Assets	5,276	6,000
Valuation allowances	(3,838)	(5,391)
Total deferred tax assets, net of valuation allowances	1,438	609
Net Deferred Tax Assets (Liabilities)	(312)	(283)
Valuation allowance increase (decrease) amount	(1,553)	657	$ (143)
Deferred Tax Liabilities, Net [Abstract]
Deferred income taxes (long-term asset)	71	59
Deferred income taxes (long-term liability)	(383)	(342)
Net Deferred Tax Assets (Liabilities)	$ (312)	$ (283)