Employee Benefit Plans (Components of AOCI and Regulatory Assets and Liabilities) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 25
Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	3
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	111
Prior service (credit) cost	1
Pension Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	13
Prior service (credit) cost	0
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	5
Prior service (credit) cost	(28)
Other Postretirement Plans | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	1
Prior service (credit) cost	$ 1