Contingencies and Commitments - Narrative (Detail) - USD ($) $ in Millions		3 Months Ended
	Nov. 01, 2020	Jun. 30, 2021		Dec. 31, 2020	[1]	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill		$ 73,758	[1]	$ 73,734		$ 81,882
Berkshire Hathaway Energy [Member] | Dominion Energy, Inc. [Member] | Cove Point [Member] | General Partner [Member]
Business Acquisition [Line Items]
Variable interest entity, ownership percentage	100.00%
Berkshire Hathaway Energy [Member] | Dominion Energy, Inc. [Member] | Cove Point [Member] | Limited Partner [Member]
Business Acquisition [Line Items]
Variable interest entity, ownership percentage	25.00%
Berkshire Hathaway Energy [Member] | Dominion Energy, Inc. [Member] | First Acquisition Agreement [Member]
Business Acquisition [Line Items]
Business acquisition, date of acquisition	Nov. 01, 2020
Payment for acquisition of business	$ 2,500
Fair value of assets acquired	13,400
Fair value of liabilities assumed	7,000
Goodwill	1,700
Fair value of liabilities including assumptions of debt	5,600
Berkshire Hathaway Energy [Member] | Dominion Energy, Inc. [Member] | First Acquisition Agreement [Member] | Limited Partner [Member]
Business Acquisition [Line Items]
Noncontrolling interest attributable to limited partnership	$ 3,900
Berkshire Hathaway Energy [Member] | Dominion Energy, Inc. [Member] | Second Acquisition Agreement [Member]
Business Acquisition [Line Items]
Payment for acquisition of business		$ 1,300

[1] Net of accumulated goodwill impairments of $11.0 billion as of June 30, 2021 and December 31, 2020.