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Quarterly Financial Data (Unaudited) (Unusual or Infrequently Occurring Items) (Details) - USD ($) $ in Millions | 2 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2016 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Oct. 31, 2016
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | $ (31) | $ (16) | $ (20) | $ (17) | $ (34) | $ (23) | $ (30) | $ (16) | $ (84) | $ (103) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  | (402) | (282) | $ (18) |
Sale of Retired Plant |  |  |  |  | 107 |  |  |  |  | 107 |  |  |
Severance Costs |  | (187) |  |  |  |  |  |  |  | (187) | (15) | (118) |
Income (Loss) From Discontinued Operations, net of tax |  | 20 | 4 | (5) |  | (2) | (2) | (2) |  | 19 | (6) | (408) |
Tax Act |  |  |  |  |  |  |  |  |  | (20) | 112 |  |
Total |  | (225) | (106) | (199) | (341) | 27 | (242) | (30) | (16) | (871) | (261) |  |
Regulatory Impairments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Asset Impairment Charges |  | (60) | (93) |  | (55) |  |  |  |  | (208) |  |  |
Regulatory settlements [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  | (179) | (86) | (23) | (135) |  |  | (265) | (158) |  |
Commercial Renewables Impairment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Asset Impairment Charges |  |  |  |  |  | (18) | (84) |  |  |  | (102) |  |
Impacts of the Tax Act [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Tax Act |  | 53 | 3 |  | (76) | 102 |  |  |  | (20) | 102 |  |
Duke Energy Carolinas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | (1) | (2) | (2) | (4) | (5) | (5) | (6) | (4) | (9) | (20) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  | (192) |  | (1) |
Severance Costs |  | (102) |  |  |  |  |  |  |  | (102) | (2) | (39) |
Tax Act |  |  | (1) |  |  | (15) |  |  |  | (1) | (15) |  |
Total |  | (103) | (3) | (181) | (23) | (20) | (5) | (6) | (4) | (310) | (35) |  |
Duke Energy Carolinas [Member] | Regulatory settlements [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  | (179) | (19) |  |  |  |  | (198) |  |  |
Progress Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | (2) | (1) | (3) | (4) | (6) | (6) | (7) | (4) | (10) | (23) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  | (87) | (156) | (7) |
Severance Costs |  | (69) |  |  |  |  |  |  |  | (69) | (2) | (40) |
Income (Loss) From Discontinued Operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 2 |
Tax Act |  | (19) | (5) |  | (1) | 246 |  |  |  | (25) | 246 |  |
Total |  | (150) | (6) | (3) | (72) | 217 | (141) | (7) | (4) | (231) | 65 |  |
Progress Energy [Member] | Regulatory Impairments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Asset Impairment Charges |  | (60) |  |  |  |  |  |  |  | (60) |  |  |
Progress Energy [Member] | Regulatory settlements [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  |  | (67) | (23) | (135) |  |  | (67) | (158) |  |
Duke Energy Progress [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | (1) | (1) | (2) | (2) | (4) | (4) | (4) | (2) | (6) | (14) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  | (33) | (19) | (1) |
Severance Costs |  | (52) |  |  |  |  |  |  |  | (52) | (1) | (23) |
Tax Act |  | (15) | (4) |  |  | 40 |  |  |  | (19) | 40 |  |
Total |  | (68) | (5) | (2) | (69) | 13 | (4) | (4) | (2) | (144) | 3 |  |
Duke Energy Progress [Member] | Regulatory settlements [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  |  | (67) | (23) |  |  |  | (67) | (23) |  |
Duke Energy Florida [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | (1) |  | (1) | (2) | (2) | (2) | (3) | (2) | (4) | (9) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  | (54) | (138) | (6) |
Severance Costs |  | (17) |  |  |  |  |  |  |  | (17) | (1) | (17) |
Tax Act |  | 2 | (2) |  |  | 226 |  |  |  |  | 226 |  |
Total |  | (76) | (2) | (1) | (2) | 224 | (137) | (3) | (2) | (81) | 82 |  |
Duke Energy Florida [Member] | Regulatory Impairments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Asset Impairment Charges |  | (60) |  |  |  |  |  |  |  | (60) |  |  |
Duke Energy Florida [Member] | Regulatory settlements [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Impairments |  |  |  |  |  |  | (135) |  |  |  | (135) |  |
Duke Energy Ohio [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | (6) |  | (5) | (3) | (2) | (2) | (1) | (1) | (14) | (6) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  |  | (1) |  |
Sale of Retired Plant |  |  |  |  | (107) |  |  |  |  | (107) |  |  |
Severance Costs |  | (6) |  |  |  |  |  |  |  | (6) |  | (3) |
Income (Loss) From Discontinued Operations, net of tax |  |  |  |  |  |  | (1) |  |  |  | (1) | 36 |
Tax Act |  | (2) |  |  |  | 23 |  |  |  | (2) | 23 |  |
Total |  | (14) |  | (5) | (110) | 21 | (2) | (1) | (1) | (129) | 17 |  |
Duke Energy Indiana [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  |  | (2) |  |  | (1) | (2) | (2) | (1) | (2) | (6) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  | (30) | (18) | (8) |
Severance Costs |  | (7) |  |  |  |  |  |  |  | (7) | (1) | $ (7) |
Tax Act |  |  |  |  |  | (55) |  |  |  |  | (55) |  |
Total |  | (7) | (2) |  |  | (56) | (2) | (2) | (1) | (9) | (61) |  |
Piedmont Natural Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Costs to achieve mergers, integration costs |  | (22) | (11) | (9) | (6) | (19) | (8) | (13) | (6) | (48) | (46) |  |
Asset Impairment Charges |  |  |  |  |  |  |  |  |  |  | (7) |  |
Severance Costs | $ (3) | (2) |  |  |  |  |  |  |  | (2) | (9) |  | $ (19)
Tax Act |  |  |  |  |  |  |  |  |  |  | 12 |  |
Total |  | $ (24) | $ (11) | $ (9) | $ (6) | (17) | $ (8) | $ (13) | $ (6) | $ (50) | (44) |  |
Piedmont Natural Gas [Member] | Impacts of the Tax Act [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information Disclosure [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Tax Act |  |  |  |  |  | $ 2 |  |  |  |  | $ 2 |  |

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