Commitments and Contingencies (Narrative) (Details) $ in Millions								1 Months Ended	9 Months Ended		12 Months Ended
	Oct. 11, 2016 USD ($)	Sep. 23, 2016 USD ($)	Feb. 08, 2016 USD ($)	Mar. 10, 2015 USD ($)	Feb. 02, 2014 T gal	Aug. 10, 2011	Aug. 09, 2011	Feb. 29, 2008	Sep. 30, 2016 USD ($) plant Claims	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Aug. 18, 2014 gal	Mar. 31, 2014 USD ($)
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual									$ 110.0		$ 166.0
Progress Energy Merger Shareholder Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Gain contingency, unrecorded amount									$ 27.0
Brazil Expansion Lawsuit [Member]
Valuation and Qualifying Accounts [Abstract]
Obligation to expand installed generation capacity, percent						15.00%	15.00%	15.00%
NCDEQ State Enforcement Actions [Member]
Valuation and Qualifying Accounts [Abstract]
Number of Plants with No Disputed Facts | plant									7
Number of Plants with Ash Basins | plant									14
Potential Groundwater Claims [Member]
Valuation and Qualifying Accounts [Abstract]
Number of Plants with Ash Basins | plant									14
Antitrust Lawsuit [Member]
Valuation and Qualifying Accounts [Abstract]
Litigation Settlement, Expense										$ 81.0
Duke Energy Carolinas [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual									$ 11.0		11.0
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member]
Valuation and Qualifying Accounts [Abstract]
Civil Penalty Assessed			$ 6.8
Litigation Settlement Amount		$ 6.0
Duke Energy Carolinas [Member] | Groundwater Violation [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency, Damages Paid, Value									1.0
Duke Energy Carolinas [Member] | Asbestos Issue [Member]
Valuation and Qualifying Accounts [Abstract]
Asbestos-related injuries and damages reserves									512.0		536.0
Reinsurance retention policy, excess retention, amount reinsured									814.0
Probable insurance recoveries									$ 567.0		599.0
Duke Energy Carolinas [Member] | Asbestos Issue [Member] | Non Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | Claims									120
Asbestos-related injuries and damages reserves									$ 32.0
Duke Energy Carolinas [Member] | Asbestos Issue [Member] | Malignant Asbestos Claim [Member]
Valuation and Qualifying Accounts [Abstract]
Loss contingency, pending claims, number | Claims									78
Asbestos-related injuries and damages reserves									$ 14.0
Duke Energy Carolinas [Member] | Minimum [Member] | North Carolina Ash Basins [Member] | Dan River [Member]
Valuation and Qualifying Accounts [Abstract]
Coal ash released, in tons | T					30,000
Basin water released, in gallons | gal					24,000,000
Duke Energy Carolinas [Member] | Maximum [Member] | North Carolina Ash Basins [Member] | Dan River [Member]
Valuation and Qualifying Accounts [Abstract]
Coal ash released, in tons | T					39,000
Basin water released, in gallons | gal					27,000,000
Progress Energy [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual									54.0		54.0
Duke Energy Progress [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual									8.0		6.0
Duke Energy Progress [Member] | Groundwater Violation [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency, Damages Paid, Value									6.0
Duke Energy Progress [Member] | Groundwater Violation [Member] | L V Sutton Plant [Member]
Valuation and Qualifying Accounts [Abstract]
Civil Penalty Assessed				$ 25.0
Duke Energy Florida [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual									30.0		31.0
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Gain contingency, unrecorded amount									54.0
Loss Contingency, Damages Sought, Original Amount													$ 510.0
Loss Contingency, Damages Awarded, Value									30.0
Gain Contingency, Dismissed Amount									54.0
Duke Energy Ohio [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency Accrual									$ 5.0		80.0
Duke Energy Ohio [Member] | W.C. Beckjord Station [Member]
Valuation and Qualifying Accounts [Abstract]
Gallons of Fuel Released | gal												9,000
Duke Energy Ohio [Member] | Antitrust Lawsuit [Member]
Valuation and Qualifying Accounts [Abstract]
Litigation Settlement Amount											$ 81.0
Litigation Settlement, Expense										$ 81.0
Subsequent Event [Member] | Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]
Valuation and Qualifying Accounts [Abstract]
Loss Contingency, Damages Sought, Original Amount	$ 482.0
Loss contingency, damages sought, value	$ 424.0