Employee Benefit Plans (Benefit Obligation in Excess of Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	$ 5,970	$ 4,978
Fair value of plan assets	4,838	4,553
Pension Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	0	0
Fair value of plan assets	0	0
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	1,564	1,233
Fair value of plan assets	1,385	1,158
Other Postretirement Plans | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	320	147
Fair value of plan assets	$ 288	$ 132