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			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenue	$ 3,432	$ 3,332	[1]	$ 9,935	$ 9,734	[2]
Purchased gas	232	191	[1]	996	818	[2]
Electric fuel and other energy-related purchases	1,107	1,009	[1]	2,933	2,816	[2]
Interest and related charges	217	197	[1]	648	618	[2]
Other income	86	56	[1]	222	174	[2]
Income from continuing operations including noncontrolling interests before income tax expense	903	410	[1]	2,086	1,653	[2]
Income tax expense	(305)	(143)	[1]	(709)	(578)	[2]
Income from continuing operations including noncontrolling interests	598	267	[1]	1,377	1,075	[2]
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	(10)			88
Income tax expense	4			(35)
Income from continuing operations including noncontrolling interests	(6)			53
Unrealized gains and losses on investment securities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income	(16)			(80)
Impairment	1			6
Income from continuing operations including noncontrolling interests before income tax expense	(15)			(74)
Income tax expense	5			28
Income from continuing operations including noncontrolling interests	(10)			(46)
Unrecognized pension and other postretirement benefit costs | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs				(6)
Actuarial losses	23			79
Income from continuing operations including noncontrolling interests before income tax expense	23			73
Income tax expense	(9)			(29)
Income from continuing operations including noncontrolling interests	14			44
Commodity contracts | Deferred gains and losses on derivatives-hedging activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating Revenue	(24)			31
Purchased gas	5			39
Electric fuel and other energy-related purchases	3			6
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	$ 6			$ 12

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

[2] Net of $43 million and $57 million tax for the three months ended September 30, 2013 and 2012, respectively, and net of $21 million and $(28) million tax for the nine months ended September 30, 2013 and 2012, respectively.