Acquisitions and Dispositions (Schedule of Results of Operations of Disposal Groups Reported As Discontinued Operations) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of assets and other charges				$ 195		$ 2,105		$ 1,520
Asset retirement obligations				5,473	[1]	5,583	[1]	5,184
Income tax expense (benefit) from discontinued operations				188		$ (204)		$ 142
GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Loss associated with cash flow hedges of debt-related items		$ 237
Loss associated with cash flow hedges of debt-related items after tax		$ 178
Income tax expense (benefit) from discontinued operations				$ (17)
Q-Pipe Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Benefit associated with the termination	$ 25
Supply Header Project | GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of assets and other charges			$ 482
Asset impairment charges after tax			359
Atlantic Coast Pipeline Project | GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Asset retirement obligations			$ 75

[1] Includes $179 million and $198 million reported in other current liabilities at December 31, 2020 and 2021, respectively