Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Sep. 30, 2012
Regulatory Assets and Liabilities
Current regulatory assets	$ 559	$ 774
Non-current regulatory assets	9,945	11,127
Regulatory assets	10,504	11,901
Current regulatory liabilities	208	191
Non-current regulatory liabilities	4	109
Regulatory liabilities	212	300
Fuel cost adjustment tax equivalents
Regulatory Assets and Liabilities
Current regulatory liabilities	176	173
Fuel cost adjustment receivable/payable
Regulatory Assets and Liabilities
Current regulatory liabilities	25	0
Unrealized gains/losses on commodity derivatives
Regulatory Assets and Liabilities
Current regulatory liabilities	7	18
Non-current regulatory liabilities	4	109
Deferred nuclear generating units
Regulatory Assets and Liabilities
Current regulatory assets	237	237
Non-current regulatory assets	295	473
Unrealized gains/losses on commodity derivatives
Regulatory Assets and Liabilities
Current regulatory assets	176	310
Non-current regulatory assets	137	335
Environmental agreements
Regulatory Assets and Liabilities
Current regulatory assets	74	87
Non-current regulatory assets	219	237
Environmental cleanup costs - Kingston ash spill
Regulatory Assets and Liabilities
Current regulatory assets	72	72
Non-current regulatory assets	738	797
Fuel cost adjustment receivable/payable
Regulatory Assets and Liabilities
Current regulatory assets	0	68
Deferred pension costs and other post-retirement benefits costs
Regulatory Assets and Liabilities
Non-current regulatory assets	5,237	5,517
Unrealized losses on interest rate derivatives
Regulatory Assets and Liabilities
Non-current regulatory assets	867	1,332
Nuclear decommissioning costs
Regulatory Assets and Liabilities
Non-current regulatory assets	922	914
Construction costs
Regulatory Assets and Liabilities
Non-current regulatory assets	619	619
Non-nuclear decommissioning costs
Regulatory Assets and Liabilities
Non-current regulatory assets	573	550
Other non-current regulatory assets
Regulatory Assets and Liabilities
Non-current regulatory assets	$ 338	$ 353

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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

+ Details

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

+ Details

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- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 405

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

+ References

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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.24)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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