Income Taxes (Reconciliation Of Effective Income Tax Rate From Continuing Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Income Taxes [Abstract]
Income tax at Federal statutory rate, value	$ 29	$ 33
State income taxes, net of Federal effect, value	4	5
Asset removal costs, value	(3)	(1)
Cross-border energy lease investments, value	(1)	(1)
Change in estimates and interest related to uncertain and effectively settled tax positions, value	(13)	1
Investment tax credits, value	(1)	(1)
Permanent differences related to deferred compensation, value	(1)	(2)
Consolidated income tax expense related to continuing operations	$ 14	$ 34
Income tax at Federal statutory rate, percentage	35.00%	35.00%
State income taxes, net of Federal effect, percentage	4.90%	5.00%
Assets removal costs, percentage	(3.70%)	(0.70%)
Cross-border energy lease investments, percentage	(1.20%)	(1.20%)
Change in estimates and interest related to uncertain and effectively settled tax positions, percentage	(15.90%)	1.20%
Investment tax credits, percentage	(1.20%)	(1.20%)
Permanent differences related to deferred compensation, percentage	(1.20%)	(2.20%)
Other, net, percentage	0.40%	(0.50%)
Consolidated income tax expense related to continuing operations	17.10%	35.40%

Changes In Estimates And Interest Related To Uncertain Tax Positions

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Income Tax Rate Change In Estimates And Interest Related To Uncertain Tax Positions

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Income Tax Reconciliation, Asset Removal Costs

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Payments For Removal Costs In Percentage

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to other deductions received under enacted tax laws not otherwise listed in the existing taxonomy.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to rents and other costs from operating leases under enacted tax laws.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to all other items not otherwise listed in the existing taxonomy.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate that can be explained by the state and local income tax expense or benefit, net of the federal tax benefit (expense) thereon, recorded during the period.

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The sum of the differences between the effective income tax rate and domestic federal statutory income tax rate that can be explained by all tax credits generated or utilized under enacted tax laws during the period.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to pretax Income or Loss from continuing operations; income tax expense or benefit may include interest and penalties on tax uncertainties based on the entity's accounting policy.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to other deductions received under enacted tax laws not otherwise listed in the existing taxonomy.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to rents and other costs from operating leases under enacted tax laws.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to state and local income tax expense or benefit.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to tax credits.

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