Nature of Operations (Narrative) (Detail)	Jun. 30, 2020	Dec. 31, 2019
White River Hub
Subsidiary Sale Of Stock [Line Items]
Percentage ownership in total units		50.00%
White River Hub | Dominion Energy Gas Holdings, LLC
Subsidiary Sale Of Stock [Line Items]
Percentage ownership in total units	50.00%
Iroquois | Dominion Energy Gas Holdings, LLC
Subsidiary Sale Of Stock [Line Items]
Percentage ownership in total units	50.00%