Acquisitions and Dispositions (Proposed Acquisition Of SCANA) (Narrative) (Detail) $ in Millions	1 Months Ended
	Jan. 31, 2018 USD ($)
SCANA
Business Acquisition And Dispositions [Line Items]
Common stock agreed to issue	66.90%
Business combination, liability incurred	$ 575
One-time rate credit to electric service customers, period within closing	90 days
Discount on existing customers	7.00%
Period to recognize reduction to SCE&C electric service customers bills	8 years
Combination debt outstanding	$ 7,000
SCANA | Termination Fee Paid By Dominion to SCANA
Business Acquisition And Dispositions [Line Items]
Contract termination fee	280
SCANA | Termination Fee Paid to Dominion
Business Acquisition And Dispositions [Line Items]
Contract termination fee	240
SCANA | Up-front Payment Arrangement | Electric Service Customers
Business Acquisition And Dispositions [Line Items]
Business combination, liability incurred	1,300
V C Summer Unit
Business Acquisition And Dispositions [Line Items]
Business combination cost related to exclusion from rate recovery	1,700
Columbia Energy
Business Acquisition And Dispositions [Line Items]
Business combination cost related to exclusion from rate recovery	$ 180