Accumulated Other Comprehensive Income (Schedule of Reclassifications out of AOCI by Component Net of Tax) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenue	$ 2,980	$ 3,005	[1]	$ 6,503	$ 6,402
Purchased gas	297	215	[1]	764	627
Electric fuel and other energy-related purchases	875	895	[1]	1,826	1,807
Interest and related charges	203	209	[1]	431	421
Other income	49	44	[1]	136	118
Income from continuing operations including noncontrolling interests before income tax expense	394	463	[1]	1,183	1,243
Income tax expense	(116)	(166)	[1]	(404)	(435)
Income from continuing operations including noncontrolling interests	278	297	[1]	779	808
Deferred gains and losses on derivatives-hedging activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations including noncontrolling interests before income tax expense	(26)			98
Income tax expense	9			(39)
Income from continuing operations including noncontrolling interests	(17)			59
Unrealized gains and losses on investment securities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income	(17)			(64)
Impairment	3			5
Income from continuing operations including noncontrolling interests before income tax expense	(14)			(59)
Income tax expense	5			23
Income from continuing operations including noncontrolling interests	(9)			(36)
Unrecognized pension and other postretirement benefit costs | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs	(6)			(6)
Actuarial losses	27			56
Income from continuing operations including noncontrolling interests before income tax expense	21			50
Income tax expense	(11)			(20)
Income from continuing operations including noncontrolling interests	10			30
Commodity contracts | Deferred gains and losses on derivatives-hedging activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenue	(29)			55
Purchased gas				34
Electric fuel and other energy-related purchases				3
Interest rate contracts | Deferred gains and losses on derivatives-hedging activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges	$ 3			$ 6

[1] Recast to reflect Brayton Point and Kincaid as discontinued operations, as discussed in Note 3.