Investments in Debt and Equity Securities (Realized Gains and Losses) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
FV-NI:
Realized gains	$ 23	$ 35
Realized losses	65	30
AFS:
Realized gains	20	10
Realized losses	6	11
Duke Energy Carolinas
FV-NI:
Realized gains	9	23
Realized losses	45	21
AFS:
Realized gains	12	9
Realized losses	5	10
Progress Energy
FV-NI:
Realized gains	14	12
Realized losses	20	9
AFS:
Realized gains	5	1
Realized losses	1	1
Duke Energy Progress
FV-NI:
Realized gains	14	10
Realized losses	20	8
AFS:
Realized gains	5	1
Realized losses	$ 1	$ 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=118939692&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=116654751&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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