Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions	12 Months Ended				9 Months Ended																																																																												12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2010		Sep. 30, 2011		Sep. 30, 2011 Derivative Asset [Member]		Sep. 30, 2011 Derivative Asset [Member] Fair Value, Inputs, Level 1 [Member]		Sep. 30, 2011 Derivative Asset [Member] Fair Value, Inputs, Level 2 [Member]		Sep. 30, 2011 Derivative Asset [Member] Fair Value, Inputs, Level 3 [Member]		Sep. 30, 2011 Derivative Asset [Member] Netting Adjustments [Member]		Sep. 30, 2011 Derivative Liability [Member]		Sep. 30, 2011 Derivative Liability [Member] Fair Value, Inputs, Level 1 [Member]		Sep. 30, 2011 Derivative Liability [Member] Fair Value, Inputs, Level 2 [Member]		Sep. 30, 2011 Derivative Liability [Member] Fair Value, Inputs, Level 3 [Member]		Sep. 30, 2011 Derivative Liability [Member] Netting Adjustments [Member]		Sep. 30, 2011 Commodity [Member]	Dec. 31, 2010 Commodity [Member]		Sep. 30, 2011 Commodity [Member] Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2010 Commodity [Member] Fair Value, Inputs, Level 1 [Member]		Sep. 30, 2011 Commodity [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2010 Commodity [Member] Fair Value, Inputs, Level 2 [Member]		Sep. 30, 2011 Commodity [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2010 Commodity [Member] Fair Value, Inputs, Level 3 [Member]		Sep. 30, 2011 Commodity [Member] Netting Adjustments [Member]		Dec. 31, 2010 Commodity [Member] Netting Adjustments [Member]		Sep. 30, 2011 Fair Value Interest Rate Contract [Member]		Dec. 31, 2010 Fair Value Interest Rate Contract [Member]		Sep. 30, 2011 Fair Value Interest Rate Contract [Member] Fair Value, Inputs, Level 1 [Member]		Dec. 31, 2010 Fair Value Interest Rate Contract [Member] Fair Value, Inputs, Level 1 [Member]		Sep. 30, 2011 Fair Value Interest Rate Contract [Member] Fair Value, Inputs, Level 2 [Member]		Dec. 31, 2010 Fair Value Interest Rate Contract [Member] Fair Value, Inputs, Level 2 [Member]		Sep. 30, 2011 Fair Value Interest Rate Contract [Member] Fair Value, Inputs, Level 3 [Member]		Dec. 31, 2010 Fair Value Interest Rate Contract [Member] Fair Value, Inputs, Level 3 [Member]		Sep. 30, 2011 Fair Value Interest Rate Contract [Member] Netting Adjustments [Member]		Dec. 31, 2010 Fair Value Interest Rate Contract [Member] Netting Adjustments [Member]		Sep. 30, 2011 Fair Value Other Assets [Member]		Dec. 31, 2010 Fair Value Other Assets [Member]		Sep. 30, 2011 Fair Value Other Assets [Member] Fair Value, Inputs, Level 1 [Member]		Dec. 31, 2010 Fair Value Other Assets [Member] Fair Value, Inputs, Level 1 [Member]		Sep. 30, 2011 Fair Value Other Assets [Member] Fair Value, Inputs, Level 2 [Member]		Dec. 31, 2010 Fair Value Other Assets [Member] Fair Value, Inputs, Level 2 [Member]		Sep. 30, 2011 Fair Value Other Assets [Member] Fair Value, Inputs, Level 3 [Member]		Dec. 31, 2010 Fair Value Other Assets [Member] Fair Value, Inputs, Level 3 [Member]		Sep. 30, 2011 Fair Value Other Assets [Member] Netting Adjustments [Member]		Dec. 31, 2010 Fair Value Other Assets [Member] Netting Adjustments [Member]		Dec. 31, 2010 Fair Value, Inputs, Level 1 [Member]		Sep. 30, 2011 Fair Value, Inputs, Level 1 [Member]		Dec. 31, 2010 Fair Value, Inputs, Level 2 [Member]		Sep. 30, 2011 Fair Value, Inputs, Level 2 [Member]		Dec. 31, 2010 Fair Value, Inputs, Level 3 [Member]		Sep. 30, 2011 Fair Value, Inputs, Level 3 [Member]		Dec. 31, 2010 Netting Adjustments [Member]		Sep. 30, 2011 Netting Adjustments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			$ 79	[1]																					$ 79	$ 106	[1]	$ 2	$ 2	[1]	$ 52	$ 72	[1]	$ 69	$ 144	[1]	$ (44)	[2]	$ (112)	[1],[2]																					$ 175	[3]	$ 166	[3]	$ 75	[3]	$ 65	[3]		[3]		[3]	$ 100	[3]	$ 101	[3]		[2],[3]		[2],[3]			$ 3	[1]			$ 51	[1]			$ 69	[1]			$ (44)	[1],[2]
Total assets	272		254																																																																														67		78		72		51		245		169		(112)	[2]	(44)	[2]
Transfer in	(45)	[4],[5],[6]			1	[4],[7]	1	[4],[7]		[4],[7]		[4],[7]		[2],[4],[7]	24	[4],[8]		[4],[8]	23	[4],[8]	1	[4],[8]		[2],[4],[8]																																																										[4],[5],[6]			(36)	[4],[5],[6]			(9)	[4],[5],[6]				[2],[4],[5],[6]
Transfer out	45	[4],[5],[6]			(1)	[4],[7]		[4],[7]	(1)	[4],[7]		[4],[7]		[2],[4],[7]	(24)	[4],[8]		[4],[8]	(1)	[4],[8]	(23)	[4],[8]		[2],[4],[8]																																																										[4],[5],[6]			9	[4],[5],[6]			36	[4],[5],[6]				[2],[4],[5],[6]
Derivative liabilities	191	[1]	121	[1]																					121	191		10	4		130	270		98	205		(117)	[2]	(288)	[2]	9	[9]	10	[9]		[9]		[9]		[9]		[9]	9	[9]	10	[9]		[2],[9]		[2],[9]																					4	[1]	10	[1]	243	[1]	152	[1]	232	[1]	76	[1]	(288)	[1],[2]	(117)	[1],[2]
Total liabilities	$ 201		$ 130																																																																														$ 4		$ 10		$ 243		$ 152		$ 242		$ 85		$ (288)	[2]	$ (117)	[2]

[1] A significant portion of the commodity derivative contracts categorized in Level 3 is valued using either an industry acceptable model or an internally developed model with observable inputs. The models also include some less readily observable inputs resulting in the classification of the entire contract as Level 3. See Note I.

[2] Amounts represent the impact of legally-enforceable master netting agreements that allow the Companies to net gain and loss positions and cash collateral held or placed with the same counterparties.

[3] Other assets are comprised of assets such as life insurance contracts within the Deferred Income Plan and Supplemental Retirement Income Plans, held in rabbi trusts.

[4] The Companies' policy is to recognize transfers into and transfers out of the levels at the end of the reporting period.

[5] Transferred from Level 2 to Level 3 because of reassessment of the levels in the fair value hierarchy within which certain inputs fall.

[6] Transferred from Level 3 to Level 2 because of availability of observable market data due to decrease in the terms of certain contracts from beyond one year as of December 31, 2009 to less than one year as of December 31, 2010.

[7] Transferred from Level 2 to Level 1 because of reassessment of the levels in the fair value hierarchy within which certain inputs fall.

[8] Transferred from Level 3 to Level 2 because of availability of observable market data due to decrease in the terms of certain contracts from beyond one year as of December 31, 2010 to less than one year as of September 30, 2011.

[9] See Note I.