Commitments and Contingencies (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) plant claim T	Dec. 31, 2017 USD ($)
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	$ 74,000,000	$ 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	$ 20,000,000	30,000,000
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	16,000,000
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves	487,000,000	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	143
Asbestos-related injuries and damages reserves	$ 37,000,000
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	58
Asbestos-related injuries and damages reserves	$ 19,000,000
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	51,000,000	55,000,000
Duke Energy Progress [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual	10,000,000	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	$ 24,000,000	$ 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