Asset Retirement Obligations (Changes to AROs) (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligations [Line Items]
Increase in estimated cash flows due to revision in timing of expected cash flows	$ 48
Decrease in estimated cash flows due to revision in timing of expected cash flows	125
Increase in cash flows associated with Milestone Unit 1	83
Cash flows charged within impairment of assets and other charges	83
Cash flows charged within impairment of assets and other charges net of tax	$ 60
Useful life extension of estimated cash flows	20 years
Other Current Liabilities
Asset Retirement Obligations [Line Items]
Asset retirement obligations	$ 434	$ 365