Commitments, Guarantees and Contingencies (Details) (USD $)	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Impact Of Boa Settlement [Abstract]
Other Operation Expense - Pretax Gain on Settlement	$ 51,000,000
Income Tax Expense	73,000,000
Net Loss After Tax on BOA and Enron Settlement	(22,000,000)
Net Income - Loss on Settlement with BOA and Enron	(22,000,000)
Deferred Income Taxes	91,000,000
Gain on Settlement with BOA and Enron	(51,000,000)	0
Settlement of Litigation with BOA and Enron	(211,000,000)	0
Accrued Taxes, Net	(18,000,000)
Acquisition of Cushion Gas from BOA	(214,000,000)	0
Cash Paid	(425,000,000)
Deferred Charges and Other Noncurrent Assets - Gas Acquired	214,000,000
Deferred Credits and Other Noncurrent Liabilities - Gas Service Liability	187,000,000
Accrued Taxes - Tax Benefit on Settlement with BOA and Enron	18,000,000
Deferred Income Taxes - Deferred Tax Benefit on Gas Service Liability	66,000,000
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Maximum Future Payments for Letters of Credit	132,000,000
Credit Agreement, 3 Year	478,000,000
Variable Rate PCBs Supported	472,000,000
Remarketed PCBs	357,000,000
Bilateral Letters of Credit	361,000,000
Remaining PCBs Held in Trust	115,000,000
New Master Lease Agreement with GE	137,000,000
Capital Leases Refinanced with GE	60,000,000
Operating Leases Refinanced with GE	77,000,000
Previously Leased Assets Purchased from GE	5,000,000
Previously Leased Assets under New Capital Lease	11,000,000
Deferred Gain and Accrued Litigation Costs	0		448,000,000
Max Percent of Unamortized Balance Guaranteed to Lessor	78.00%
Percent Limit, Unamortized Balance	78.00%
Maximum Potential Loss on Master Lease Agreements	15,000,000
Guaranteed Sales Proceeds Percentage of Fair Value to Lessor Current Term	84.00%
Guaranteed Sales Proceeds Percentage of Fair Value to Lessor End of Max Lease Term	77.00%
Expense Recorded Due to Remediation Work Remaining Provision	11,000,000
Estimated Repair of the Property Damage and Rotor Replacement Cost	408,000,000
Recoverable Amount Under the Property Insurance Policy	60,000,000
Received Partial Payments for the Cost Incurred to Repair Property Damage	203,000,000
Exclusive Right to Use Cushion Gas, in Billion Cubic Feet	55
Attorneys' Fees to BOA	20,000,000
Payment to BOA after Court Judgement	346,000,000
Proposed Civil Penalty for Violation of Federal Reporting Requirements	300,000
Proposed State Civil Penalty for Violation of Reporting Requirements	240,000
Payment Amount for Fort Wayne Lease Dispute Settlement	39,000,000
Number of Years to Pay the Fort Wayne Lease Dispute Settlement Amount	15
Deferred Gain on the 2005 Sale of Houston Pipeline Company	380,000,000
Sale Price of Houston Pipeline Company in 2005	1,000,000,000
Payment to Settle BOA Litigation	425,000,000
Capital Loss Valuation Allowance On Settlement	56,000,000
Amount Paid to Settle State Environmental Claim	75,000
Net Loss Recognized on BOA Settlement	22,000,000
Pretax Gain on BOA Settlement	51,000,000
Facility1 [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Credit Facilities,Total	1,500,000,000
Facility 2 [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Credit Facilities,Total	1,500,000,000
Replacement Facility Maturing 2016 [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Credit Facilities,Total	1,750,000,000
Letter of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Credit Facilities,Total	1,350,000,000
Southwestern Electric Power Co [Member] | Original [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount	65,000,000
Southwestern Electric Power Co [Member] | Expanded [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount	100,000,000
Indiana Michigan Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Future Minimum Lease Obligation for Remaining Railcars	16,000,000
Maximum Potential Loss on Guarantee of Return-and-Sale Option	12,000,000
Southwestern Electric Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Estimated Final Cost Mine Reclamation	58,000,000
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs	51,000,000
Amount Collected, Rider Mine Close Other Current Liabilities	1,000,000
Amount Collected Rider Mine Close Other Liabilities Noncurrent	30,000,000
Amount Collected, Rider Mine Close ARO Noncurrent	20,000,000
Future Minimum Lease Obligation for Remaining Railcars	18,000,000
Maximum Potential Loss on Guarantee of Return-and-Sale Option	13,000,000
From [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Amount Required for Relocation of the Village	95,000,000
To [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Amount Required for Relocation of the Village	$ 400,000,000