Employee Benefit Plans (Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 32	$ 29
Interest cost	72	72
Expected return on plan assets	(133)	(125)
Amortization of prior service cost (credit)	0	1
Amortization of net actuarial loss	40	28
Net periodic benefit cost (credit)	11	5
Pension Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3
Interest cost	7	7
Expected return on plan assets	(31)	(29)
Amortization of net actuarial loss	5	5
Net periodic benefit cost (credit)	(16)	(14)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	8
Interest cost	17	17
Expected return on plan assets	(29)	(28)
Amortization of prior service cost (credit)	(7)	(7)
Amortization of net actuarial loss	1	0
Net periodic benefit cost (credit)	(8)	(10)
Other Postretirement Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1
Interest cost	3	3
Expected return on plan assets	(6)	(5)
Amortization of net actuarial loss	1	0
Net periodic benefit cost (credit)	$ 0	$ (1)