Business acquisitions - Narrative (Detail) - Berkshire Hathaway Energy [Member] - Dominion Energy, Inc. [Member] - USD ($) $ in Billions		12 Months Ended
Nov. 01, 2020	Dec. 31, 2021
Cove Point [Member]
Business Acquisition [Line Items]
Variable interest entity, ownership percentage	25.00%
General Partner [Member] \| Cove Point [Member]
Business Acquisition [Line Items]
Variable interest entity, ownership percentage	100.00%
Limited Partner [Member] \| Cove Point [Member]
Business Acquisition [Line Items]
Variable interest entity, ownership percentage	25.00%
First Acquisition Agreement [Member]
Business Acquisition [Line Items]
Business acquisition, date of completed	Nov. 01, 2020
Business acquisition definitive agreement, month and year		2020-07
Payment for acquisition of business in cash after post-closing adjustments	$ 2.5
Second Acquisition Agreement [Member]
Business Acquisition [Line Items]
Business acquisition definitive agreement, month and year		2020-10
Termination of agreement, month and year		2021-07

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Business acquisition month of termination agreement.

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