Quarterly Financial Information (Schedule Of Quarterly Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Quarterly Financial Information [Abstract]
Total Operating Revenue	$ 1,234		$ 1,643		$ 1,409		$ 1,634		$ 1,517		$ 2,067		$ 1,636		$ 1,819		$ 5,920		$ 7,039		$ 7,402
Total Operating Expenses	1,143		1,448		1,207	[1]	1,485		1,429	[2],[3]	1,855	[2],[3]	1,443	[2],[3]	1,688	[2],[3]	5,283		6,415	[2],[3]	6,754
Operating Income	91		195		202		149		88		212		193		131		637		624		648
Other expenses	(62)		(60)		(53)		(53)		(115)	[4]	(197)	[4]	(84)	[4]	(78)	[4]	(228)		(474)	[4]	(1)
Income From Continuing Operations Before Income Tax Expense	29		135		149		96		(27)		15		109		53		409		150		327
Income Tax Expense Related to Continuing Operations	6	[5]	55	[5]	54	[5]	34	[5]	(41)		(6)	[6]	33	[7]	25	[8]	149	[5]	11		104
Net Income from Continuing Operations	23		80		95	[1]	62		14		21		76		28		260		139		223
(Loss) Income from Discontinued Operations, net of Income Taxes	(4)				(1)		2		19		(4)		(130)		8		(3)		(107)		12
Net Income (Loss)	$ 19		$ 80		$ 94		$ 64		$ 33		$ 17		$ (54)		$ 36		$ 257		$ 32		$ 235
Basic and Diluted Share Information
Earnings per share of common stock from Continuing Operations	$ 0.10		$ 0.35		$ 0.42		$ 0.27		$ 0.06		$ 0.09		$ 0.34		$ 0.13		$ 1.15		$ 0.62		$ 1.01
Basic and diluted (loss) earnings per share of common stock from discontinued operations	$ (0.02)						$ 0.01		$ 0.08		$ (0.01)		$ (0.58)		$ 0.03		$ (0.01)		$ (0.48)		$ 0.05
Basic and Diluted Earnings Per Share of Common Stock	$ 0.08		$ 0.35		$ 0.42		$ 0.28		$ 0.14		$ 0.08		$ (0.24)		$ 0.16		$ 1.14		$ 0.14		$ 1.06
Cash Dividends Per Common Share	$ 0.27		$ 0.27		$ 0.27		$ 0.27		$ 0.27		$ 0.27		$ 0.27		$ 0.27		$ 1.08		$ 1.08		$ 1.08

[1] Includes $39 million pre-tax ($3 million after-tax) gain from the early termination of cross-border energy leases held in trust.

[2] Includes restructuring charges of $14 million and $16 million in the third and fourth quarters, respectively.

[3] Includes expenses of $2 million and $9 million in the second and third quarters, respectively, related to the effects of Pepco divestiture-related claims.

[4] Includes debt extinguishment costs of $135 million and $54 million in the third and fourth quarters, respectively.

[5] Includes tax benefits of $14 million in the second quarter primarily associated with an interest benefit related to federal tax liabilities and a $22 million reversal of previously recognized tax benefits in the second quarter associated with the early termination of cross-border energy leases held in trust.

[6] Includes state income tax benefits of $13 million and $4 million in the third and fourth quarters, respectively, associated with the loss on extinguishment of debt and a $18 million Federal tax benefit in the fourth quarter related primarily to reversals of previously accrued interest on uncertain and effectively settled tax positions due to the final settlement with the IRS of the 1996-2002 tax years.

[7] Includes state income tax benefits of $8 million resulting from the restructuring of certain PHI subsidiaries.

[8] Includes an $8 million reversal of accrued interest income on uncertain and effectively settled state tax positions and a $4 million reversal of deferred tax assets related to the Medicare Part D subsidy, partially offset by state income tax benefits of $8 million resulting from the planned restructuring of certain PHI subsidiaries.