Regulatory Matters (Schedule of MISO Exit fees)(Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Restructuring Reserve [Roll Forward]
Balance, beginning of period	$ 64us-gaap_RestructuringReserve
Provision/adjustments	5us-gaap_RestructuringCharges
Cash reductions	(41)us-gaap_PaymentsForRestructuring
Balance, end of period	28us-gaap_RestructuringReserve
Total regulatory assets	12,157us-gaap_RegulatoryAssets	10,086us-gaap_RegulatoryAssets
Duke Energy Ohio [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	2
Provision/adjustments	5
Cash reductions	(1)
Balance, end of period	6
Total regulatory assets	561	528
Duke Energy Ohio [Member] \| RTO Realignment [Member]
Restructuring Reserve [Roll Forward]
Balance, beginning of period	95
Provision/adjustments	3
Cash reductions	(4)
Balance, end of period	94
Total regulatory assets	$ 74

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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- Definition

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

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ 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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-Name Accounting Standards Codification

-Topic 420

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-Paragraph 1

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-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

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-Name Accounting Standards Codification

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-Paragraph 1

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

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- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

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