Employee Benefit Plans (AOCI and regulatory assets and liabilities that have not been recognized as components of periodic benefit (credit) cost) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss		$ (799)	$ (474)
Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss		(123)	(99)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss		3,200	2,381
Prior service (credit) cost		4	5
Total	[1]	3,204	2,386
Amount included in AOCI		1,900	1,400
Pension Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss		458	380
Prior service (credit) cost		0	1
Total	[2]	458	381
Amount included in AOCI		167	138
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss		283	114
Prior service (credit) cost		(419)	(237)
Total	[1]	(136)	(123)
Amount included in AOCI		(103)	(90)
Other Postretirement Plans | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss		60	33
Prior service (credit) cost		7	7
Total	[2]	$ 67	$ 40

[1] As of December 31, 2016, of the $3.2 billion and $(136) million related to pension benefits and other postretirement benefits, $1.9 billion and $(103) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities. As of December 31, 2015, of the $2.4 billion and $(123) million related to pension benefits and other postretirement benefits, $1.4 billion and $(90) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities.

[2] As of December 31, 2016, of the $458 million related to pension benefits, $167 million is included in AOCI, with the remainder included in regulatory assets and liabilities; the $67 million related to other postretirement benefits is included entirely in regulatory assets and liabilities. As of December 31, 2015, of the $381 million related to pension benefits, $138 million is included in AOCI, with the remainder included in regulatory assets and liabilities; the $40 million related to other postretirement benefits is included entirely in regulatory assets and liabilities.