Contingencies and Commitments - Narrative (Detail) - Berkshire Hathaway Energy [Member] - Dominion Energy, Inc. [Member] $ in Billions		1 Months Ended	9 Months Ended
	Oct. 05, 2020 USD ($)	Jul. 31, 2020 USD ($) Bcfe mi	Sep. 30, 2020
Long Term Purchase Commitment [Line Items]
Business acquisition, contingent acquisition description			to acquire substantially all of Dominion’s natural gas transmission and storage business, which includes more than 7,700 miles of natural gas transmission pipelines, about 900 billion cubic feet of operated natural gas storage capacity and partial ownership of a liquefied natural gas export, import and storage facility.
Natural gas storage capacity acquired | Bcfe		900
Business combination, contingent consideration acquisition price		$ 4.0
Business acquisition, asset-related long-term debt		$ 5.7
First Acquisition Agreement [Member] | Subsequent Event [Member]
Long Term Purchase Commitment [Line Items]
Business acquisition, date of acquisition	Oct. 05, 2020
Payment for acquisition of business in cash	$ 2.7
Business acquisition assumed debt	$ 5.3
Business acquisition, date of completed	Nov. 01, 2020
Second Acquisition Agreement [Member] | Subsequent Event [Member]
Long Term Purchase Commitment [Line Items]
Business acquisition, date of acquisition	Oct. 05, 2020
Payment for acquisition of business in cash	$ 1.3
Business acquisition assumed debt	$ 0.4
Minimum [Member]
Long Term Purchase Commitment [Line Items]
Business acquisition, length of pipelines acquired | mi		7,700