Acquisitions and Dispositions (Schedule of Preliminary Allocation of Purchase Price to Assets Acquired and Liabilities Assumed) (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2019	Dec. 31, 2018
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Goodwill	[1]	$ 7,381	$ 7,395		$ 4,859
SCANA
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Total current assets	[2]		1,782
Investments	[3]		224
Property, plant and equipment	[4],[5]		11,006
Goodwill			2,609
Regulatory assets	[6]		3,940
Other deferred charges and other assets, including intangible assets	[7]		430
Total Assets			19,991
Total current liabilities	[8]		1,556
Total outstanding debt			6,707	$ 6,900
Deferred income taxes			1,068
Regulatory liabilities			2,706
Other deferred credits and other liabilities	[9]		1,115
Total Liabilities			13,152
Total purchase price	[10]		$ 6,839

[1] Goodwill amounts do not contain any accumulated impairment losses.

[2] Includes $389 million of cash, restricted cash and equivalents, of which $115 million is considered restricted.

[3] Includes $31 million for equity method investments. The fair value adjustment on the equity method investments is considered to be equity method goodwill and is not amortized.

[4] Includes $105 million of certain property, plant and equipment associated with the NND Project for which Dominion Energy committed to forgo recovery in accordance with the SCANA Merger Approval Order. As a result, Dominion Energy’s Consolidated Statements of Income for the year ended December 31, 2019 include a charge of $105 million ($79 million after-tax), included in impairment of assets and other charges (reflected in the Corporate and Other segment).

[5] Nonregulated property, plant and equipment, excluding land, will be depreciated on a straight-line basis over the remaining useful lives of such property, primarily ranging from 5 to 78 years.

[6] Includes $258 million of certain income tax-related regulatory assets associated with the NND Project for which Dominion Energy committed to forgo recovery in accordance with the SCANA Merger Approval Order. See Note 5 for additional information.

[7] Intangible assets have an estimated weighted-average amortization period of approximately five years.

[8] Includes $40 million outstanding under letters of credit advances, which were repaid in January 2019, as well as $173 million outstanding commercial paper under various credit facilities. All such credit facilities were terminated in 2019.

[9] Includes a $379 million pension and other postretirement benefit liability.

[10] Includes stock-based compensation awards with a fair value of $21 million.