The accumulated balance of costs for qualifying projects used to calculate AFUDC.

No definition available.

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- Definition

Interest on funds invested in capital projects has been capitalized only for projects with (1) an expected total project cost of $1.0 billion or more, and (2) an estimated construction period of at least three years in duration.

+ References

No definition available.

+ Details

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- Definition

The amortization period.

+ References

No definition available.

+ Details

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- Definition

Depreciation [Line Items]

+ References

No definition available.

+ Details

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- Definition

The minimum construction period necessary in order to capitalize allowance for funds used during construction.

+ References

No definition available.

+ Details

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- Definition

Number of units to be idled.

+ References

No definition available.

+ Details

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- Definition

Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735

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- Definition

For each income statement presented, the amount charged to expense for amortization of capitalized computer software costs.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128487-111756

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-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

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+ Details

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- Definition

The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

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-Section 50

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

+ Details

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- Definition

The other noncash expense, not otherwise specified in the taxonomy, charged against earnings in the period to allocate the cost of tangible and intangible assets over their remaining economic lives.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.3)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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- Definition

Amount capitalized of allowance for funds used during construction.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 835

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Allowance for Funds Used during Construction

-URI http://asc.fasb.org/extlink&oid=6504829

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Composite depreciation rate for public utility plants in service.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Property, Plant, and Equipment, and Depreciation (Details) $ in Millions	12 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2011 Units
Property, Plant, and Equipment, and Depreciation
Depreciation	$ 1,700	$ 1,600	$ 1,400
Composite depreciation rate for completed plant	3.71%	3.42%	3.12%
Accelerated depreciation	$ 383	$ 206	$ 49
Capital leases	94	102
Allowance for funds used during construction	214	175
AFUDC minimum total project cost	$ 1,000
Minimum construction period	3 years
Accumulated balance of qualifying projects	$ 4,100
Capitalized software amortization period	5 years
Unamortized computer software costs	$ 18	22
Amortization expense of capitalized computer software costs	38	31	$ 31
Electricity Generation Plant, Non-Nuclear [Member]
Property, Plant, and Equipment, and Depreciation
Capital leases	$ 94	$ 102
Nuclear
Property, Plant, and Equipment, and Depreciation
Composite depreciation rate for completed plant	2.81%	2.90%	2.86%
Coal-fired
Property, Plant, and Equipment, and Depreciation
Composite depreciation rate for completed plant	5.50%	4.37%	3.47%
Hydroelectric
Property, Plant, and Equipment, and Depreciation
Composite depreciation rate for completed plant	1.30%	1.44%	1.30%
Gas and oil-fired
Property, Plant, and Equipment, and Depreciation
Composite depreciation rate for completed plant	3.18%	3.23%	3.21%
Transmission
Property, Plant, and Equipment, and Depreciation
Composite depreciation rate for completed plant	2.78%	2.76%	2.76%
Other
Property, Plant, and Equipment, and Depreciation
Composite depreciation rate for completed plant	8.65%	8.40%	8.14%
Environmental Agreements
Property, Plant, and Equipment, and Depreciation
Number of units to be idled \| Units				18