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, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Fuel Oils [Member]		Mar. 31, 2011 Fuel Oils [Member]		Mar. 31, 2012 Natural Gas [Member]	Mar. 31, 2011 Natural Gas [Member]	Mar. 31, 2012 Power [Member]		Mar. 31, 2011 Power [Member]		Mar. 31, 2011 Uranium [Member]	Mar. 31, 2012 Uranium [Member]	Dec. 31, 2011 Uranium [Member]
Beginning balance	$ 4		$ 51		$ (174)	$ (148)	$ 115		$ 36		$ 2	$ (1)	$ (1)
Included in earnings	2	[1]	22	[1]			8	[1]	(3)	[1]
Included in OCI							24
Included in regulatory assets/liabilities	2		31		(28)	7	(158)		(2)		(1)
Total realized and unrealized gains (losses)	4		53		(28)	7	(126)		(5)		(1)
Purchases			1				(1)		9
Sales							1		(9)
Settlements			(9)		17	21	(14)
Transfers into Level 3	2
Transfers out of Level 3	(1)				185		1
Ending balance	9		96			(120)	(24)		31		1	(1)	(1)
Change in unrealized gains (losses) related to assets/liabilities still held	$ 3		$ 69			$ 7	$ (133)		$ 9		$ (1)

[1] Net gains and losses on fuel oils 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.