Acquisitions and Dispositions (Schedule of Results of Operations Reported As Discontinued Operations) (Detail) - Dominion Energy Gas Holdings, LLC $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net income (loss) from discontinued operations	$ 54
East Ohio
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue	229
Depreciation and amortization	21
Other operating expenses	148
Other income	18
Interest and related charges	10
Income tax expense	14
Net income (loss) from discontinued operations	54
DGP
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue	45
Depreciation and amortization	1
Other operating expenses	$ 44