Fair Value Measurements (Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Heating Oil [Member]
Beginning balance	$ 68		$ 29		$ 51		$ 60
Included in earnings	(7)	[1]	4	[1]	10	[1]	(6)	[1]
Included in regulatory assets/liabilities	(12)		8		10		(3)
Total realized and unrealized gains (losses)	(19)		12		20		(9)
Purchases	1				3		32
Sales	(1)				(1)
Settlements	(19)		(3)		(43)		(45)
Ending balance	30		38		30		38
Change in unrealized gains (losses) related to assets/liabilities still held	(22)		13		4		(5)
Natural Gas [Member]
Beginning balance	(117)		(138)		(148)		(67)
Included in regulatory assets/liabilities	(33)		(70)		(46)		(179)
Total realized and unrealized gains (losses)	(33)		(70)		(46)		(179)
Purchases	(1)		(1)				(5)
Settlements	23		27		66		69
Ending balance	(128)		(182)		(128)		(182)
Change in unrealized gains (losses) related to assets/liabilities still held	(29)		(65)		(34)		(116)
Power [Member]
Beginning balance	117		54		36		38
Included in earnings		[1]	20	[1]	(18)	[1]	44	[1]
Included in OCI	(7)		5		(2)		11
Included in regulatory assets/liabilities	25		(15)		89		(8)
Total realized and unrealized gains (losses)	18		10		69		47
Purchases	2		(2)		61		36
Sales	(1)		11		(17)		6
Settlements	(18)		(24)		(34)		(53)
Transfers into Level 3	(2)				(1)		(1)
Transfers out of Level 3	(2)		(1)				(25)
Ending balance	114		48		114		48
Change in unrealized gains (losses) related to assets/liabilities still held	22		(10)		77		6
Uranium [Member]
Beginning balance	(2)		(4)		2		(2)
Included in regulatory assets/liabilities			2		(4)
Total realized and unrealized gains (losses)			2		(4)
Settlements	1				1
Ending balance	(1)		(2)		(1)		(2)
Change in unrealized gains (losses) related to assets/liabilities still held			$ 1		$ (2)

[1] Net gains and losses on heating oil and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.