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		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss)		$ 130	$ 54	$ 281	$ (519)
Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax		(34)		(34)		$ (35)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net		(2)		(2)
Net gain (loss) from commodity hedging and trading activities [Member] | Commodity contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss)	[1]	130	54	281	(114)
Interest expense and related charges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss)	[2]				(128)
Interest expense and related charges [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss)	[2]	0	0	0
Reorganization Items [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss)		$ 0	$ 0	$ 0	$ (277)

[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 6).