Derivative Instruments And Hedging Activities (Cash Flow Hedges Included In Accumulated Other Comprehensive Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax			$ 89
Portion Expected to be Reclassified to Income during the Next 12 Months			49
Energy Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	29	[1]	78	[1]
Portion Expected to be Reclassified to Income during the Next 12 Months	23	[1]	48	[1]
Maximum Term	29 months	[1]	41 months	[1]
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	10		11
Portion Expected to be Reclassified to Income during the Next 12 Months	$ 1		$ 1
Maximum Term	248 months		260 months

[1] The unrealized derivative losses recorded in AOCL relate to forecasted natural gas and electricity physical purchases which are used to supply retail natural gas and electricity contracts that are in gain positions and subject to accrual accounting. Under accrual accounting, no asset is recorded on the balance sheet and the purchase cost is not recognized until the period of distribution.