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Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | $ 37 | $ 45 | $ 74 | $ 90
Interest cost on projected benefit obligation | 82 | 75 | 165 | 150
Expected return on plan assets | (143) | (140) | (286) | (280)
Amortization of actuarial loss (gain) | 25 | 33 | 49 | 66
Amortization of prior service (credit) cost | (8) | (8) | (16) | (16)
Net periodic costs | (7) | 5 | (14) | 10
Duke Energy Carolinas [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 12 | 15 | 24 | 30
Interest cost on projected benefit obligation | 21 | 18 | 41 | 36
Expected return on plan assets | (37) | (37) | (75) | (74)
Amortization of actuarial loss (gain) | 5 | 7 | 11 | 14
Amortization of prior service (credit) cost | (2) | (2) | (4) | (4)
Net periodic costs | (1) | 1 | (3) | 2
Progress Energy [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 10 | 13 | 21 | 26
Interest cost on projected benefit obligation | 26 | 22 | 52 | 46
Expected return on plan assets | (45) | (43) | (89) | (88)
Amortization of actuarial loss (gain) | 9 | 11 | 18 | 22
Amortization of prior service (credit) cost |  | (1) | (1) | (2)
Net periodic costs |  | 2 | 1 | 4
Duke Energy Progress [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 6 | 8 | 12 | 15
Interest cost on projected benefit obligation | 12 | 10 | 24 | 21
Expected return on plan assets | (21) | (21) | (44) | (42)
Amortization of actuarial loss (gain) | 3 | 5 | 6 | 10
Amortization of prior service (credit) cost | (1) | (1) | (1) | (1)
Net periodic costs | (1) | 1 | (3) | 3
Duke Energy Florida [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 6 | 6 | 10 | 11
Interest cost on projected benefit obligation | 13 | 12 | 27 | 25
Expected return on plan assets | (22) | (23) | (44) | (46)
Amortization of actuarial loss (gain) | 6 | 6 | 12 | 12
Amortization of prior service (credit) cost | (1) | (1) | (1) | (1)
Net periodic costs | 2 |  | 4 | 1
Duke Energy Ohio [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 1 | 1 | 2 | 2
Interest cost on projected benefit obligation | 4 | 4 | 9 | 9
Expected return on plan assets | (6) | (7) | (14) | (14)
Amortization of actuarial loss (gain) |  | 1 | 1 | 2
Net periodic costs | (1) | (1) | (2) | (1)
Duke Energy Indiana [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 2 | 3 | 4 | 5
Interest cost on projected benefit obligation | 7 | 6 | 13 | 12
Expected return on plan assets | (10) | (11) | (21) | (21)
Amortization of actuarial loss (gain) | 1 | 2 | 3 | 4
Amortization of prior service (credit) cost | (1) |  | (1) |
Net periodic costs | (1) |  | (2) |
Piedmont Natural Gas [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | 2 | 2 | 3 | 4
Interest cost on projected benefit obligation | 3 | 3 | 6 | 6
Expected return on plan assets | (6) | (6) | (11) | (12)
Amortization of actuarial loss (gain) | 1 | 3 | 3 | 6
Amortization of prior service (credit) cost | (2) | (3) | (5) | (6)
Net periodic costs | $ (2) | $ (1) | $ (4) | $ (2)

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: 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 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) 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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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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/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 3: 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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- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: 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 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -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 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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