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Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions | 9 Months Ended
--- | ---
Sep. 30, 2018 | Sep. 30, 2017
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | $ 81 | $ 98
Provisions/adjustments | 7 | (1)
Cash reductions | (20) | (13)
Balance at end of period | 68 | 84
Environmental exit costs, reasonably possible additional loss | 57 |
Duke Energy Carolinas [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 10 | 10
Provisions/adjustments | 3 | 2
Cash reductions | (2) | (2)
Balance at end of period | 11 | 10
Environmental exit costs, reasonably possible additional loss | 17 |
Progress Energy [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 15 | 18
Provisions/adjustments | 2 | 1
Cash reductions | (5) | (3)
Balance at end of period | 12 | 16
Duke Energy Progress [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 3 | 3
Provisions/adjustments | 3 |
Cash reductions | (1) |
Balance at end of period | 5 | 3
Duke Energy Florida [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 12 | 14
Provisions/adjustments | (1) | 1
Cash reductions | (4) | (3)
Balance at end of period | 7 | 12
Duke Energy Ohio [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 47 | 59
Provisions/adjustments | 3 | (3)
Cash reductions | (12) | (7)
Balance at end of period | 38 | 49
Environmental exit costs, reasonably possible additional loss | 30 |
Duke Energy Indiana [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 5 | 10
Provisions/adjustments | 1 | (2)
Cash reductions | (1) | (1)
Balance at end of period | 5 | 7
Piedmont Natural Gas [Member] |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Balance at beginning of period | 2 | 1
Provisions/adjustments |  | 1
Cash reductions | 0 |
Balance at end of period | 2 | $ 2
Environmental exit costs, reasonably possible additional loss | $ 2 |

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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 + Details
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