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
	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenue	$ 3,523	$ 3,397	[1]
Purchased gas	467	412	[1]
Electric fuel and other energy-related purchases	951	912	[1]
Interest and related charges	228	212	[1]
Other income	87	74	[1]
Other operations and maintenance	623	607	[1]
Income from continuing operations including noncontrolling interests before income tax expense	789	780	[1]
Income tax expense	(288)	(269)	[1]
Income from continuing operations including noncontrolling interests	501	511	[1]
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	124
Income tax expense	(48)
Income from continuing operations including noncontrolling interests	76
Unrealized gains and losses on investment securities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income	(47)
Impairment	2
Income from continuing operations including noncontrolling interests before income tax expense	(45)
Income tax expense	18
Income from continuing operations including noncontrolling interests	(27)
Unrecognized pension and other postretirement benefit costs | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance	29
Income from continuing operations including noncontrolling interests before income tax expense	29
Income tax expense	(9)
Income from continuing operations including noncontrolling interests	20
Commodity contracts | Deferred gains and losses on derivatives-hedging activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenue	84
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

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