Asset Retirement Obligations (ARO Rollforward) (Details) $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	$ 13,318
Accretion expense	408
Liabilities settled	(540)
Liabilities incurred in the current year	17
Revision in estimates of cash flows	451
Balance at end of period	13,654
Duke Energy Carolinas
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	5,734
Accretion expense	195
Liabilities settled	(151)
Revision in estimates of cash flows	(4)
Balance at end of period	5,774
Progress Energy
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	6,471
Accretion expense	187
Liabilities settled	(333)
Revision in estimates of cash flows	30
Balance at end of period	6,355
Duke Energy Progress
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	5,893
Accretion expense	171
Liabilities settled	(293)
Revision in estimates of cash flows	29
Balance at end of period	5,800
Duke Energy Florida
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	578
Accretion expense	16
Liabilities settled	(40)
Revision in estimates of cash flows	1
Balance at end of period	555
Duke Energy Ohio
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	80
Accretion expense	3
Liabilities settled	(1)
Revision in estimates of cash flows	9
Balance at end of period	91
Duke Energy Indiana
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	832
Accretion expense	22
Liabilities settled	(56)
Revision in estimates of cash flows	416
Balance at end of period	1,214
Piedmont Natural Gas
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	17
Balance at end of period	$ 17

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848

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Amount of asset retirement obligations incurred during the period.

+ References

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Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ References

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Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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