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Derivatives and Hedging (Narrative) (Details) - USD ($)
$ in Millions
1 Months Ended
Apr. 30, 2020
Mar. 31, 2020
Call option    
Derivative [Line Items]    
Aggregate notional amount   305,000
Put option    
Derivative [Line Items]    
Aggregate notional amount   305,000
Not Designated as Hedging Instruments | Duke Energy Florida | Equity Securities Contracts | Subsequent event    
Derivative [Line Items]    
Proceeds liquidation of options $ 7