Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011
Energy supply and hedging activities credit exposure total	$ 152
Makeup of net credit exposure counterparties	58
Makeup of net credit exposure primarily with commodity exchange	53
Independent system operators	39
Number of contracts considered derivatives	1,705
Non-Investment Grade Counterparties [Member]
Makeup of net credit exposure primarily with commodity exchange	$ 2