Employee Benefit Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 34	$ 28	$ 69	$ 57
Interest cost	87	78	173	155
Expected return on plan assets	(161)	(139)	(320)	(278)
Amortization of prior service cost (credit)	1	1	1	1
Amortization of net actuarial loss	41	27	81	55
Settlements			1	0
Net periodic benefit cost (credit)	2	(5)	5	(10)
Pension Benefits | Dominion Energy Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4	8	7
Interest cost	8	7	15	15
Expected return on plan assets	(36)	(34)	(71)	(67)
Amortization of prior service cost (credit)	0	0	0	0
Amortization of net actuarial loss	4	4	8	7
Net periodic benefit cost (credit)	(20)	(19)	(40)	(38)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	8	13	16
Interest cost	14	17	30	34
Expected return on plan assets	(31)	(30)	(63)	(59)
Amortization of prior service cost (credit)	(13)	(7)	(25)	(14)
Amortization of net actuarial loss	3	2	6	3
Settlements			0	0
Net periodic benefit cost (credit)	(21)	(10)	(39)	(20)
Other Postretirement Benefits | Dominion Energy Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2	2	3
Interest cost	3	4	6	7
Expected return on plan assets	(6)	(7)	(12)	(12)
Amortization of prior service cost (credit)	(1)	0	(1)	0
Amortization of net actuarial loss	0	1	1	1
Net periodic benefit cost (credit)	$ (3)	$ 0	$ (4)	$ (1)