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Acquisitions and Sales of Other Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended |  |  |  | 0 Months Ended | 3 Months Ended |  |  |  | 3 Months Ended |  |  |  | 3 Months Ended |  | 0 Months Ended | 3 Months Ended |  | 0 Months Ended | 3 Months Ended |
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Mar. 31, 2013 | Mar. 31, 2012 | Dec. 31, 2012 | Jul. 02, 2012 | Jan. 12, 2012 | Jan. 12, 2012 Wabash Valley Power Association [Member] | Mar. 31, 2013 Ibener [Member] | Apr. 30, 2013 Ibener [Member] | Mar. 31, 2013 Duke Energy Carolinas [Member] | Dec. 31, 2012 Duke Energy Carolinas [Member] | Mar. 31, 2013 Progress Energy [Member] | Mar. 31, 2012 Progress Energy [Member] | Dec. 31, 2012 Progress Energy [Member] | Mar. 31, 2013 Duke Energy Progress [Member] | Dec. 31, 2012 Duke Energy Progress [Member] | Mar. 31, 2013 Duke Energy Florida [Member] | Mar. 31, 2012 Duke Energy Florida [Member] | Dec. 31, 2012 Duke Energy Florida [Member] | Jan. 12, 2012 Duke Energy Ohio [Member] | Mar. 31, 2013 Duke Energy Ohio [Member] | Mar. 31, 2012 Duke Energy Ohio [Member] | Dec. 31, 2012 Duke Energy Ohio [Member] | Jan. 12, 2012 Duke Energy Indiana [Member] | Mar. 31, 2013 Duke Energy Indiana [Member] | Mar. 31, 2012 Duke Energy Indiana [Member] | Dec. 31, 2012 Duke Energy Indiana [Member]
Significant Acquisitions and Disposals [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Adjusted conversion ratio, after reverse stock split adjustment |  |  |  | 87.083% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of outstanding earned stock compensation awards |  |  |  | $ 62 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total estimated purchase price |  |  |  | 18,071 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve the merger | 10 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impairment of other long-lived assets | 0 | 407 |  |  |  |  |  |  |  |  | 0 | 0 |  |  |  | 0 | 0 |  |  | 0 | 2 |  |  | 0 | 400 |
Transfer of Vermillion Generating Station |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (28) |  |  | 0 | 26 |
Proceeds from sale of interest in jointly owned utility plant |  |  |  |  |  | 14 |  |  |  |  |  |  |  |  |  |  |  |  | 82 |  |  |  | 68 |  |  |
Sale of ownership interest in Vermillion Generating Station |  |  |  |  | 75.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available capacity |  |  |  |  |  |  |  |  |  |  |  |  |  | (722) |  | (587) |  |  |  |  |  |  |  |  |  |
Cash collateral returned |  |  |  |  |  |  |  | 192 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash paid |  |  |  |  |  |  | 415 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment | 23,122 |  |  |  |  |  | 383 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Intangibles |  |  |  |  |  |  | 30 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred tax |  |  |  |  |  |  | 57 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Working capital |  |  |  |  |  |  | 6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bridge loan |  |  |  |  |  |  | 190 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill | 12,477 |  |  |  |  |  | 53 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revolving loan under credit agreement |  |  |  |  |  |  | 200 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current maturities of long-term debt | $ 3,323 |  | $ 3,110 |  |  |  |  |  | $ 406 | $ 406 | $ 718 |  | $ 843 | $ 407 | $ 407 | $ 10 |  | $ 435 |  | $ 259 |  | $ 261 |  | $ 405 |  | $ 405
Percentage of loan collateralized by cash deposits |  |  |  |  |  |  | 101.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument year due |  |  |  |  |  |  | Dec. 20, 2013 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument maturity date option to extend |  |  |  |  |  |  | 13 years 0 months 0 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e1043-128460 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141R -Paragraph 59 -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. + Details
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- Definition Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 + Details
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- Definition The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230 + Details
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- Definition Value of other real estate transferred from the entity's other real estate in noncash transactions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 32 -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. + Details
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