Acquisitions and Dispositions (Disposition of Gas Transmission & Storage Operations to BHE) (Narrative) (Detail) - USD ($)		12 Months Ended
	Nov. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 31, 2020	Jul. 31, 2020
Business Acquisition And Dispositions [Line Items]
Income tax expense	$ 336,000,000	$ 83,000,000	$ 209,000,000	$ 522,000,000
GT&S Transaction
Business Acquisition And Dispositions [Line Items]
Operating revenue		4,000,000	$ 6,000,000	$ 6,000,000
Derivative payment					$ 165,000,000
GT&S Transaction | BHE
Business Acquisition And Dispositions [Line Items]
Disposal group, total value of consideration						$ 10,000,000,000
Disposal group, cash consideration		222,000,000				$ 4,000,000,000.0
Cash proceeds received	2,700,000,000
Disposal group, recognized a pre-tax gain upon closing	127,000,000
Goodwill write-off	$ 1,400,000,000
GT&S Transaction | BHE | Transition Service Agreement
Business Acquisition And Dispositions [Line Items]
Operating revenue		4,000,000
GT&S Transaction | BHE | Cove Point
Business Acquisition And Dispositions [Line Items]
Percentage ownership in total units	50.00%
Disposal group, initial fair value	$ 2,800,000,000
GT&S Transaction | BHE | General Partner Interest
Business Acquisition And Dispositions [Line Items]
Percentage ownership in total units						100.00%
GT&S Transaction | BHE | Limited Partner Interests
Business Acquisition And Dispositions [Line Items]
Percentage ownership in total units						25.00%
Q-Pipe Transaction | BHE
Business Acquisition And Dispositions [Line Items]
Disposal group, cash consideration					$ 1,300,000,000
Disposal group, recognized a pre-tax gain upon closing		450,000,000
Goodwill write-off		191,000,000
Disposal group, including discontinued operation, deposits	$ 1,300,000,000
Disposal group, recognized a gain on disposal after tax		$ 320,000,000