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Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plans - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | $ 41 | $ 42 | $ 124 | $ 116
Interest cost on projected benefit obligation | 67 | 77 | 202 | 242
Expected return on plan assets | (143) | (140) | (429) | (426)
Amortization of actuarial loss | 32 | 28 | 96 | 77
Amortization of prior service credit | (8) | (8) | (24) | (24)
Amortization of settlement charges | 11 |  | 16 |
Net periodic pension costs |  | (1) | (15) | (15)
Duke Energy Carolinas |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 12 | 13 | 38 | 37
Interest cost on projected benefit obligation | 16 | 17 | 47 | 58
Expected return on plan assets | (36) | (36) | (108) | (111)
Amortization of actuarial loss | 7 | 6 | 21 | 17
Amortization of prior service credit | (2) | (2) | (6) | (6)
Amortization of settlement charges | 6 |  | 8 |
Net periodic pension costs | 3 | (2) |  | (5)
Progress Energy |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 12 | 13 | 36 | 34
Interest cost on projected benefit obligation | 21 | 24 | 64 | 76
Expected return on plan assets | (48) | (45) | (143) | (134)
Amortization of actuarial loss | 10 | 10 | 30 | 28
Amortization of prior service credit |  | (1) | (2) | (2)
Amortization of settlement charges | 5 |  | 6 |
Net periodic pension costs |  | 1 | (9) | 2
Duke Energy Progress |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 6 | 7 | 20 | 19
Interest cost on projected benefit obligation | 10 | 10 | 29 | 34
Expected return on plan assets | (22) | (22) | (66) | (66)
Amortization of actuarial loss | 4 | 4 | 13 | 10
Amortization of prior service credit |  |  | (1) | (1)
Amortization of settlement charges | 5 |  | 6 |
Net periodic pension costs | 3 | (1) | 1 | (4)
Duke Energy Florida |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 5 | 5 | 16 | 15
Interest cost on projected benefit obligation | 12 | 14 | 35 | 41
Expected return on plan assets | (25) | (22) | (76) | (66)
Amortization of actuarial loss | 6 | 6 | 17 | 18
Amortization of prior service credit |  |  | (1) | (1)
Amortization of settlement charges | 1 |  | 1 |
Net periodic pension costs | (1) | 3 | (8) | 7
Duke Energy Ohio |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 1 | 1 | 3 | 3
Interest cost on projected benefit obligation | 4 | 5 | 12 | 14
Expected return on plan assets | (7) | (7) | (21) | (21)
Amortization of actuarial loss | 2 | 2 | 5 | 3
Net periodic pension costs |  | 1 | (1) | (1)
Duke Energy Indiana |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 2 | 2 | 6 | 6
Interest cost on projected benefit obligation | 6 | 6 | 17 | 19
Expected return on plan assets | (11) | (11) | (32) | (32)
Amortization of actuarial loss | 3 | 3 | 9 | 6
Amortization of prior service credit |  |  | (1) | (1)
Amortization of settlement charges | 1 |  | 1 |
Net periodic pension costs | 1 |  |  | (2)
Piedmont Natural Gas |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 1 | 1 | 4 | 4
Interest cost on projected benefit obligation | 2 | 2 | 7 | 8
Expected return on plan assets | (5) | (5) | (16) | (16)
Amortization of actuarial loss | 2 | 2 | 7 | 5
Amortization of prior service credit | (2) | (2) | (7) | (7)
Amortization of settlement charges | 1 |  | 1 |
Net periodic pension costs | $ (1) | $ (2) | $ (4) | $ (6)

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