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Commitments and Contingencies (Narrative 2) (Details) - Spent Nuclear Fuel Matters
$ in Millions
Jun. 18, 2018
USD ($)
Duke Energy Progress  
Gain Contingencies [Line Items]  
Gain contingency, unrecorded amount $ 100
Duke Energy Florida  
Gain Contingencies [Line Items]  
Gain contingency, unrecorded amount $ 200