Commodity And Other Derivative Contractual Assets And Liabilities (Derivative (Income Statement Presentation) and Derivative type (Income Statement Presentation of Loss Reclassified from Accumulated OCI into Income)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended				9 Months Ended					3 Months Ended				9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Interest rate swaps [Member]	Dec. 31, 2012 Interest rate swaps [Member]	Sep. 30, 2013 Net gain (loss) from commodity hedging and trading activities [Member]		Sep. 30, 2012 Net gain (loss) from commodity hedging and trading activities [Member]		Sep. 30, 2013 Net gain (loss) from commodity hedging and trading activities [Member]		Sep. 30, 2012 Net gain (loss) from commodity hedging and trading activities [Member] Commodity contracts [Member]		Sep. 30, 2012 Interest expense and related charges [Member]	Sep. 30, 2013 Interest expense and related charges [Member] Interest rate swaps [Member]		Sep. 30, 2012 Interest expense and related charges [Member] Interest rate swaps [Member]		Sep. 30, 2013 Interest expense and related charges [Member] Interest rate swaps [Member]	Sep. 30, 2013 Cash Flow Hedging [Member] Interest rate swaps [Member]	Sep. 30, 2012 Cash Flow Hedging [Member] Interest rate swaps [Member]	Sep. 30, 2013 Cash Flow Hedging [Member] Interest rate swaps [Member]	Sep. 30, 2012 Cash Flow Hedging [Member] Interest rate swaps [Member]	Sep. 30, 2013 Cash Flow Hedging [Member] Depreciation and amortization [Member] Interest rate swaps [Member]	Sep. 30, 2012 Cash Flow Hedging [Member] Depreciation and amortization [Member] Interest rate swaps [Member]	Sep. 30, 2013 Cash Flow Hedging [Member] Depreciation and amortization [Member] Interest rate swaps [Member]	Sep. 30, 2012 Cash Flow Hedging [Member] Depreciation and amortization [Member] Interest rate swaps [Member]	Sep. 30, 2013 Cash Flow Hedging [Member] Interest expense and related charges [Member] Interest rate swaps [Member]	Sep. 30, 2012 Cash Flow Hedging [Member] Interest expense and related charges [Member] Interest rate swaps [Member]	Sep. 30, 2013 Cash Flow Hedging [Member] Interest expense and related charges [Member] Interest rate swaps [Member]	Sep. 30, 2012 Cash Flow Hedging [Member] Interest expense and related charges [Member] Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss)	$ 351	$ (283)	$ 487	$ (391)			$ 98	[1]	$ (95)	[1]	$ 54	[1]	$ 130	[1]	$ (521)	$ 253	[2]	$ (188)	[2]	$ 433
Income statement presentation of loss reclassified from accumulated OCI into income	(2)	(2)	(6)	(7)																	(2)	(2)	(8)	(8)	(1)	(1)	(2)	(2)	(1)	(1)	(6)	(6)
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax					(37)	(42)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net					$ (2)

[1] Amount represents changes in fair value of positions in the derivative portfolio during the period, as realized amounts related to positions settled are assumed to equal reversals of previously recorded unrealized amounts.

[2] Includes unrealized mark-to-market net gain (loss) as well as the net realized effect on interest paid/accrued, both reported in "Interest Expense and Related Charges" (see Note 12).