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Asset Retirement Obligations (NDTF Information) (Details) - USD ($)
$ in Millions
Jun. 30, 2019
Dec. 31, 2018
Asset Retirement Obligations [Line Items]    
Legally restricted NDTF investments, fair value $ 6,327 $ 5,579
Duke Energy Carolinas [Member]    
Asset Retirement Obligations [Line Items]    
Legally restricted NDTF investments, fair value 3,574 3,133
Duke Energy Progress [Member]    
Asset Retirement Obligations [Line Items]    
Legally restricted NDTF investments, fair value 2,753 2,446
Progress Energy [Member]    
Asset Retirement Obligations [Line Items]    
Legally restricted NDTF investments, fair value $ 2,753 $ 2,446