Commitments and Contingencies (PurchPower)(Details) - Public Utilities Purchased Power [Member] $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Duke Energy Progress [Member]
Unconditional Purchase Obligations [Abstract]
2018	$ 68
2019	68
2020	51
2021	52
2022	30
Thereafter	239
Total	$ 508
Duke Energy Progress [Member] \| Minimum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2019
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	15.00%
Duke Energy Progress [Member] \| Maximum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2031
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	100.00%
Duke Energy Florida [Member]
Unconditional Purchase Obligations [Abstract]
2018	$ 357
2019	374
2020	394
2021	378
2022	376
Thereafter	770
Total	$ 2,649
Duke Energy Florida [Member] \| Minimum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2021
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	81.00%
Duke Energy Florida [Member] \| Maximum [Member]
Unconditional Purchase Obligations [Abstract]
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	2043
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased	100.00%

No definition available.

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Share of plant output being purchased under a long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.D)
-URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77896938&loc=d3e25336-109308

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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