Employee Benefit Plans (Pension plan and other postretirement plan assets that are measured at fair value and included in the Level 3 fair value category) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits
Actual return on plan assets:
Fair value of plan assets at end of year	$ 6,480	$ 6,113	$ 5,553
Pension Benefits | Level 3
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	1,124	1,190	1,285
Actual return on plan assets:
Relating to assets still held at the reporting date	126	166	105
Relating to assets sold during the period	(115)	(122)	(62)
Purchases	145	153	129
Sales	(247)	(263)	(267)
Fair value of plan assets at end of year	1,033	1,124	1,190
Pension Benefits | Level 3 | Real estate:
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	227	321	304
Actual return on plan assets:
Relating to assets still held at the reporting date	40	15	21
Relating to assets sold during the period	(18)	(36)	(8)
Purchases	0	6	35
Sales	(40)	(79)	(31)
Fair value of plan assets at end of year	209	227	321
Pension Benefits | Level 3 | Private equity
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	530	456	448
Actual return on plan assets:
Relating to assets still held at the reporting date	70	98	46
Relating to assets sold during the period	(67)	(48)	(41)
Purchases	135	115	79
Sales	(150)	(91)	(76)
Fair value of plan assets at end of year	518	530	456
Pension Benefits | Level 3 | Debt
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	180	192	243
Actual return on plan assets:
Relating to assets still held at the reporting date	12	32	17
Relating to assets sold during the period	(26)	(34)	(11)
Purchases	10	32	15
Sales	(32)	(42)	(72)
Fair value of plan assets at end of year	144	180	192
Pension Benefits | Level 3 | Hedge funds
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	187	221	290
Actual return on plan assets:
Relating to assets still held at the reporting date	4	21	21
Relating to assets sold during the period	(4)	(4)	(2)
Purchases	0	0	0
Sales	(25)	(51)	(88)
Fair value of plan assets at end of year	162	187	221
Pension Benefits | Dominion Gas Holdings, LLC
Actual return on plan assets:
Fair value of plan assets at end of year	1,510	1,403	1,254
Pension Benefits | Dominion Gas Holdings, LLC | Level 3
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	258	268	285
Actual return on plan assets:
Relating to assets still held at the reporting date	31	40	26
Relating to assets sold during the period	(26)	(26)	(13)
Purchases	32	33	27
Sales	(54)	(57)	(57)
Fair value of plan assets at end of year	241	258	268
Pension Benefits | Dominion Gas Holdings, LLC | Level 3 | Real estate:
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	52	72	68
Actual return on plan assets:
Relating to assets still held at the reporting date	9	4	6
Relating to assets sold during the period	(4)	(8)	(2)
Purchases	0	1	7
Sales	(9)	(17)	(7)
Fair value of plan assets at end of year	48	52	72
Pension Benefits | Dominion Gas Holdings, LLC | Level 3 | Private equity
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	122	103	99
Actual return on plan assets:
Relating to assets still held at the reporting date	17	24	12
Relating to assets sold during the period	(15)	(10)	(9)
Purchases	30	25	17
Sales	(33)	(20)	(16)
Fair value of plan assets at end of year	121	122	103
Pension Benefits | Dominion Gas Holdings, LLC | Level 3 | Debt
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	41	43	54
Actual return on plan assets:
Relating to assets still held at the reporting date	4	7	4
Relating to assets sold during the period	(6)	(7)	(2)
Purchases	2	7	3
Sales	(7)	(9)	(16)
Fair value of plan assets at end of year	34	41	43
Pension Benefits | Dominion Gas Holdings, LLC | Level 3 | Hedge funds
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	43	50	64
Actual return on plan assets:
Relating to assets still held at the reporting date	1	5	4
Relating to assets sold during the period	(1)	(1)	0
Purchases	0	0	0
Sales	(5)	(11)	(18)
Fair value of plan assets at end of year	38	43	50
Other Postretirement Plans
Actual return on plan assets:
Fair value of plan assets at end of year	1,402	1,315	1,156
Other Postretirement Plans | Level 3
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	116	124	137
Actual return on plan assets:
Relating to assets still held at the reporting date	13	8	9
Relating to assets sold during the period	(11)	5	(1)
Purchases	14	10	9
Sales	(28)	(31)	(30)
Fair value of plan assets at end of year	104	116	124
Other Postretirement Plans | Level 3 | Real estate:
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	19	24	24
Actual return on plan assets:
Relating to assets still held at the reporting date	4	(2)	1
Relating to assets sold during the period	(1)	1	0
Purchases	0	1	2
Sales	(3)	(5)	(3)
Fair value of plan assets at end of year	19	19	24
Other Postretirement Plans | Level 3 | Private equity
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	60	58	63
Actual return on plan assets:
Relating to assets still held at the reporting date	7	6	3
Relating to assets sold during the period	(7)	3	(1)
Purchases	13	7	6
Sales	(15)	(14)	(13)
Fair value of plan assets at end of year	58	60	58
Other Postretirement Plans | Level 3 | Debt
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	27	31	36
Actual return on plan assets:
Relating to assets still held at the reporting date	2	3	4
Relating to assets sold during the period	(3)	0	0
Purchases	1	2	1
Sales	(9)	(9)	(10)
Fair value of plan assets at end of year	18	27	31
Other Postretirement Plans | Level 3 | Hedge funds
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	10	11	14
Actual return on plan assets:
Relating to assets still held at the reporting date	0	1	1
Relating to assets sold during the period	0	1	0
Purchases	0	0	0
Sales	(1)	(3)	(4)
Fair value of plan assets at end of year	9	10	11
Other Postretirement Plans | Dominion Gas Holdings, LLC
Actual return on plan assets:
Fair value of plan assets at end of year	288	273	242
Other Postretirement Plans | Dominion Gas Holdings, LLC | Level 3
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	21	24	28
Actual return on plan assets:
Relating to assets still held at the reporting date	3	2	(2)
Relating to assets sold during the period	(2)	0	3
Purchases	2	1	1
Sales	(6)	(6)	(6)
Fair value of plan assets at end of year	18	21	24
Other Postretirement Plans | Dominion Gas Holdings, LLC | Level 3 | Real estate:
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	2	3	3
Actual return on plan assets:
Relating to assets still held at the reporting date	0	(1)	0
Relating to assets sold during the period	0	0	0
Purchases	0	0	0
Sales	0	0	0
Fair value of plan assets at end of year	2	2	3
Other Postretirement Plans | Dominion Gas Holdings, LLC | Level 3 | Private equity
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	12	13	15
Actual return on plan assets:
Relating to assets still held at the reporting date	2	2	(1)
Relating to assets sold during the period	(1)	0	2
Purchases	2	1	1
Sales	(3)	(4)	(4)
Fair value of plan assets at end of year	12	12	13
Other Postretirement Plans | Dominion Gas Holdings, LLC | Level 3 | Debt
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	7	8	10
Actual return on plan assets:
Relating to assets still held at the reporting date	1	1	(1)
Relating to assets sold during the period	(1)	0	1
Purchases	0	0	0
Sales	(3)	(2)	(2)
Fair value of plan assets at end of year	4	7	8
Other Postretirement Plans | Dominion Gas Holdings, LLC | Level 3 | Hedge funds
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	0	0	0
Actual return on plan assets:
Relating to assets still held at the reporting date	0	0	0
Relating to assets sold during the period	0	0	0
Purchases	0	0	0
Sales	0	0	0
Fair value of plan assets at end of year	$ 0	$ 0	$ 0