Merger Agreement (Details) (USD $) In Millions, except Share data	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Business Combinations [Abstract]
Business Acquisition, Date Of Acquisition Agreement			January 8, 2011
Merger, Description			Pursuant to the Merger Agreement, Progress Energy will be acquired by Duke Energy in a stock-for-stock transaction (the Merger) and continue as a wholly owned subsidiary of Duke Energy.
Merger share exchange ratio	2.6125		2.6125
Merger Share Exchange Ratio, Adjusted	0.87083		0.87083
Settlement Agreement, Date			September 2, 2011
Settlement Agreement, Description			Progress Energy and Duke Energy will guarantee $650 million in fuel cost savings for customers in North Carolina and South Carolina between 2012 and 2016, maintain their current level of community support for the next four years, and provide $15 million for low-income energy assistance and workforce development. The parties also agreed that direct merger-related expenses would not be recovered from customers. Recovery of merger-related employee severance costs can be requested separately.
Settlement Agreement, Fuel Savings	$ 650		$ 650
Loss Contingencies [Line Items]
Loss Contingency Estimate Of Possible Loss	14		14
Loss Contingency Unrecorded Estimate Of Possible Loss	16		16
Settlement Agreement, Low Income And Workforce Assistance	15		15
Merger and integration costs, net of tax	$ 15	$ 0	$ 36	$ 0

This element represents acquisition-related and integration-related costs incurred to effect a business combination which costs have been expensed during the period. Acquisition-related costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. Integration-related costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

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- Definition

Reflects the unrecorded, estimated amount of loss from the specified contingency as of the balance sheet date.

+ Details

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- Definition

Description of the planned business combination.

+ Details

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- Definition

Discloses the number of shares of the acquirer's stock that each share of the acquiree's stock will be converted into in conjuction with a merger.

+ Details

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- Definition

Discloses the number of shares of the acquirer's stock that each share of the acquiree's stock will be converted into in conjuction with a merger after the acquiring company's planned reverse stock split.

+ Details

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- Definition

The date the settlement agreement was filed.

+ Details

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- Definition

Description of the terms of a settlement agreement which resolved the regulatory matter.

+ Details

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- Definition

Amount of fuel savings that will be passed on to customers over five years guaranteed under the settlement agreement.

+ Details

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- Definition

Amount of low income and work force assistance guaranteed under the settlement agreement.

+ Details

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- Definition

Month, day and year when the business acquisition agreement was executed.

+ Details

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- Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14557-108349

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