Investments in Debt and Equity Securities (Realized Gains and Losses) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
FV-NI:
Realized gains	$ 140	$ 23
Realized losses	23	65
AFS:
Realized gains	18	20
Realized losses	13	6
Duke Energy Carolinas
FV-NI:
Realized gains	128	9
Realized losses	16	45
AFS:
Realized gains	13	12
Realized losses	9	5
Progress Energy
FV-NI:
Realized gains	12	14
Realized losses	7	20
AFS:
Realized gains	4	5
Realized losses	3	1
Duke Energy Progress
FV-NI:
Realized gains	12	14
Realized losses	7	20
AFS:
Realized gains	4	5
Realized losses	$ 3	$ 1

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- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized gain from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714

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Amount of realized loss from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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