Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	$ 882
Intangible Assets, Accumulated Amortization	386
Intangible Assets, Net	496us-gaap_FiniteLivedIntangibleAssetsNet
Amortization Expense
Actual, 2014	80.0us-gaap_AmortizationOfIntangibleAssets
Estimated, 2015	75
Estimated, 2016	75
Estimated, 2017	68
Estimated, 2018	51
Estimated, 2019	50
Estimated, Thereafter	136
FES
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Net	78	95
Amortization Expense
Actual, 2014	5.7
NUG contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	124
Intangible Assets, Accumulated Amortization	20
Intangible Assets, Net	104
Amortization Expense
Actual, 2014	5.0
Estimated, 2015	5
Estimated, 2016	5
Estimated, 2017	5
Estimated, 2018	5
Estimated, 2019	5
Estimated, Thereafter	79
OVEC
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	54
Intangible Assets, Accumulated Amortization	7
Intangible Assets, Net	47
Amortization Expense
Actual, 2014	2.0
Estimated, 2015	2
Estimated, 2016	2
Estimated, 2017	2
Estimated, 2018	2
Estimated, 2019	2
Estimated, Thereafter	37
Coal contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	556
Intangible Assets, Accumulated Amortization	289
Intangible Assets, Net	267
Amortization Expense
Actual, 2014	55.0
Estimated, 2015	51
Estimated, 2016	51
Estimated, 2017	45
Estimated, 2018	30
Estimated, 2019	30
Estimated, Thereafter	19
Coal contracts \| Recorded with Regulatory Offset
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	102
Intangible Assets, Net	41
Coal contracts \| Recorded with Regulatory Offset \| FES
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	40
Intangible Assets, Net	29
Customer Contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	148
Intangible Assets, Accumulated Amortization	70
Intangible Assets, Net	78
Amortization Expense
Actual, 2014	18.0
Estimated, 2015	17
Estimated, 2016	17
Estimated, 2017	16
Estimated, 2018	14
Estimated, 2019	13
Estimated, Thereafter	$ 1

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ 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)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References