Income Taxes (Effective Income Tax Rate From Continuing Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended															12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010	Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Income tax at Federal statutory rate																$ 143		$ 52	$ 114
Increases (decreases) resulting from Depreciation																		(3)	6
State income taxes, net of federal effect																22			19
State tax benefit related to prior years' asset dispositions																(4)			(13)
Cross-border energy lease investments																16		(5)	(6)
Change in estimates and interest related to uncertain and effectively settled tax positions																(11)		(6)	(1)
Investment tax credits																(4)		(4)	(4)
Deferred tax basis adjustments																2		(3)	(4)
Reversal of valuation allowance																		(8)
Change in state deferred tax balances as a result of restructuring																		(6)
Other, net																(15)		(6)	(7)
Consolidated Income Tax Expense Related to Continuing Operations	$ 6	[1]	$ 55	[1]	$ 54	[1]	$ 34	[1]	$ (41)	$ (6)	[2]	$ 33	[3]	$ 25	[4]	$ 149	[1]	$ 11	$ 104
Income tax at federal statutory rate																35.00%		35.00%	35.00%
Increases (decreases) resulting from Depreciation																		(2.00%)	1.80%
State income taxes, net of federal effect																5.40%			5.70%
State tax benefits related to prior years' asset dispositions																(1.00%)			(4.00%)
Cross-border energy lease investments																3.90%		(3.30%)	(1.70%)
Change in estimates and interest related to uncertain and effectively settled tax positions																(2.70%)		(4.00%)	(0.40%)
Investment tax credits																(1.00%)		(2.70%)	(1.20%)
Deferred tax basis adjustments																0.20%		(2.00%)	(1.20%)
Reversal of valuation allowance																		(5.30%)
Change in state deferred tax balances as a result of restructuring																		(4.00%)
Other, net																(3.40%)		(4.40%)	(2.20%)
Consolidated income tax expense related to continuing operations																36.40%		7.30%	31.80%

[1] Includes tax benefits of $14 million in the second quarter primarily associated with an interest benefit related to federal tax liabilities and a $22 million reversal of previously recognized tax benefits in the second quarter associated with the early termination of cross-border energy leases held in trust.

[2] Includes state income tax benefits of $13 million and $4 million in the third and fourth quarters, respectively, associated with the loss on extinguishment of debt and a $18 million Federal tax benefit in the fourth quarter related primarily to reversals of previously accrued interest on uncertain and effectively settled tax positions due to the final settlement with the IRS of the 1996-2002 tax years.

[3] Includes state income tax benefits of $8 million resulting from the restructuring of certain PHI subsidiaries.

[4] Includes an $8 million reversal of accrued interest income on uncertain and effectively settled state tax positions and a $4 million reversal of deferred tax assets related to the Medicare Part D subsidy, partially offset by state income tax benefits of $8 million resulting from the planned restructuring of certain PHI subsidiaries.