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Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Pension Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Amortization of regulatory asset | $ 4 | $ 4 | $ 5
Pension Plan | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 165 | 158 |
Service cost | 157 | 150 | 182
Interest cost | 269 | 317 | 299
Expected return on plan assets | (572) | (567) | (559)
Amortization of prior service credit | 128 | 108 | 132
Amortization of prior service cost (credit) | (32) | (32) | (32)
Amortization of settlement charges | 18 | 6 |
Net periodic costs | (24) | (10) | 22
Pension Plan | Duke Energy Carolinas | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 51 | 49 |
Service cost | 49 | 47 | 58
Interest cost | 62 | 75 | 72
Expected return on plan assets | (145) | (147) | (147)
Amortization of prior service credit | 28 | 24 | 29
Amortization of prior service cost (credit) | (8) | (8) | (8)
Amortization of settlement charges | 9 | 2 |
Net periodic costs | (3) | (5) | 4
Pension Plan | Progress Energy | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 48 | 46 |
Service cost | 46 | 43 | 51
Interest cost | 85 | 100 | 94
Expected return on plan assets | (190) | (178) | (178)
Amortization of prior service credit | 41 | 39 | 44
Amortization of prior service cost (credit) | (3) | (3) | (3)
Amortization of settlement charges | 7 | 1 |
Net periodic costs | (12) | 5 | 8
Pension Plan | Duke Energy Progress | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 27 | 26 |
Service cost | 26 | 25 | 29
Interest cost | 38 | 45 | 43
Expected return on plan assets | (87) | (88) | (85)
Amortization of prior service credit | 18 | 15 | 21
Amortization of prior service cost (credit) | (2) | (2) | (2)
Amortization of settlement charges | 6 | 1 |
Net periodic costs | 0 | (3) | 6
Pension Plan | Duke Energy Florida | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 21 | 20 |
Service cost | 20 | 18 | 22
Interest cost | 46 | 54 | 50
Expected return on plan assets | (101) | (89) | (91)
Amortization of prior service credit | 23 | 24 | 23
Amortization of prior service cost (credit) | (1) | (1) | (1)
Amortization of settlement charges | 1 | 0 |
Net periodic costs | (11) | 8 | 3
Pension Plan | Duke Energy Ohio |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Amortization of regulatory asset | 2 | 2 | 2
Pension Plan | Duke Energy Ohio | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 5 | 4 |
Service cost | 4 | 4 | 5
Interest cost | 15 | 18 | 17
Expected return on plan assets | (28) | (28) | (28)
Amortization of prior service credit | 6 | 4 | 5
Amortization of prior service cost (credit) | 0 | 0 | 0
Amortization of settlement charges | 0 | 2 |
Net periodic costs | (2) | 0 | (1)
Pension Plan | Duke Energy Indiana | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 9 | 9 |
Service cost | 8 | 8 | 11
Interest cost | 22 | 26 | 23
Expected return on plan assets | (42) | (43) | (42)
Amortization of prior service credit | 12 | 8 | 10
Amortization of prior service cost (credit) | (2) | (2) | (2)
Amortization of settlement charges | 1 | 0 |
Net periodic costs | 0 | (2) | 0
Pension Plan | Piedmont | Qualified Plan |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 6 | 5 |
Service cost | 5 | 5 | 7
Interest cost | 9 | 10 | 11
Expected return on plan assets | (21) | (22) | (22)
Amortization of prior service credit | 9 | 8 | 11
Amortization of prior service cost (credit) | (9) | (9) | (10)
Amortization of settlement charges | 1 | 0 |
Net periodic costs | (5) | (8) | (3)
Other Post-Retirement Benefit Plans |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 4 | 4 | 6
Interest cost | 23 | 30 | 28
Expected return on plan assets | (13) | (12) | (13)
Amortization of prior service credit | 2 | 4 | 6
Amortization of prior service cost (credit) | (14) | (19) | (19)
Net periodic costs | 2 | 7 | 8
Amortization of regulatory asset | 6 | 6 | 7
Other Post-Retirement Benefit Plans | Duke Energy Carolinas |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 1 | 1 | 1
Interest cost | 5 | 7 | 7
Expected return on plan assets | (8) | (7) | (8)
Amortization of prior service credit | 0 | 2 | 3
Amortization of prior service cost (credit) | (4) | (5) | (5)
Net periodic costs | (6) | (2) | (2)
Other Post-Retirement Benefit Plans | Progress Energy |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 1 | 1 | 1
Interest cost | 10 | 12 | 12
Expected return on plan assets | 0 | 0 | 0
Amortization of prior service credit | 1 | 1 | 1
Amortization of prior service cost (credit) | (3) | (8) | (8)
Net periodic costs | 9 | 6 | 6
Other Post-Retirement Benefit Plans | Duke Energy Progress |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 0 | 0 | 0
Interest cost | 5 | 7 | 6
Expected return on plan assets | 0 | 0 | 0
Amortization of prior service credit | 0 | 0 | 1
Amortization of prior service cost (credit) | (1) | (1) | (1)
Net periodic costs | 4 | 6 | 6
Other Post-Retirement Benefit Plans | Duke Energy Florida |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 0 | 1 | 1
Interest cost | 4 | 5 | 6
Expected return on plan assets | 0 | 0 | 0
Amortization of prior service credit | 1 | 1 | 0
Amortization of prior service cost (credit) | (2) | (7) | (7)
Net periodic costs | 3 | 0 | 0
Other Post-Retirement Benefit Plans | Duke Energy Ohio |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 0 | 0 | 1
Interest cost | 1 | 1 | 1
Expected return on plan assets | 0 | 0 | 0
Amortization of prior service credit | 0 | 0 | 0
Amortization of prior service cost (credit) | (1) | (1) | (1)
Net periodic costs | 0 | 0 | 1
Amortization of regulatory asset | 1 | 2 | 2
Other Post-Retirement Benefit Plans | Duke Energy Indiana |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 1 | 1 | 1
Interest cost | 2 | 3 | 3
Expected return on plan assets | 0 | 0 | 0
Amortization of prior service credit | 4 | 4 | 4
Amortization of prior service cost (credit) | (1) | (1) | (1)
Net periodic costs | 6 | 7 | 7
Other Post-Retirement Benefit Plans | Piedmont |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |
Service cost | 0 | 0 | 1
Interest cost | 1 | 1 | 1
Expected return on plan assets | (2) | (1) | (2)
Amortization of prior service credit | 0 | 0 | 0
Amortization of prior service cost (credit) | (2) | (2) | (2)
Net periodic costs | $ (3) | $ (2) | $ (2)

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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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