Commitments and Contingencies (Narrative) (Details)	1 Months Ended	6 Months Ended
	Jul. 31, 2018 USD ($)	Jun. 30, 2018 USD ($) plant claim T	Dec. 31, 2017 USD ($)
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		$ 68,000,000	$ 88,000,000
Coal Ash Insurance Coverage Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Number of NC and SC Plants with Ash Basins | plant		15
NCDEQ State Enforcement Actions [Member]
Valuation and Qualifying Accounts [Abstract]
Number of Plants with No Disputed Facts | plant		7
Number of NC Plants with Ash Basins | plant		14
Number of Plants with Disputed Facts | plant		7
Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Goodwill Payment		$ 5,000
Water Bill Stipend Period		25 years
Duke Energy Carolinas [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		$ 15,000,000	30,000,000
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		10,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves		466,000,000	489,000,000
Reinsurance retention policy, excess retention, amount reinsured		797,000,000
Probable insurance recoveries		$ 585,000,000	585,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Non-Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | claim		120
Asbestos-related injuries and damages reserves		$ 29,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | claim		47
Asbestos-related injuries and damages reserves		$ 12,000,000
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		52,000,000	55,000,000
Duke Energy Progress [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		11,000,000	13,000,000
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		3,000,000
Duke Energy Progress [Member] | Spent Nuclear Fuels [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount			48,000,000
Litigation Settlement, Amount Awarded from Other Party		$ 48,000,000
Duke Energy Progress [Member] | Gypsum Supply Agreements [Member]
Valuation and Qualifying Accounts [Abstract]
Minimum Amount of Gypsum To Be Supplied | T		50,000
Duke Energy Florida [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual		$ 25,000,000	24,000,000
Duke Energy Florida [Member] | Spent Nuclear Fuels [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount			$ 25,000,000
Litigation Settlement, Amount Awarded from Other Party		21,000,000
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount		54,000,000
Loss Contingency, Damages Sought, Original Amount		510,000,000
Loss Contingency, Damages Awarded, Value		30,000,000
Gain Contingency, Dismissed Amount		54,000,000
Loss Contingency Damages Awarded and Interest, Value		34,000,000
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member]
Valuation and Qualifying Accounts [Abstract]
Gain Contingency, Unrecorded Amount		$ 43,000,000
Subsequent Event [Member] | Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency, Damages Paid, Value	$ 34,000,000