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Employee Benefit Plans (Sensitivity to Changes in Assumed Health Care Cost Trend Rates) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service and interest costs - 1 Percentage Point Increase $ 1
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 22
Effect on total service and interest costs - 1 Percentage Point Decrease (1)
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (20)
Duke Energy Carolinas [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 5
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (5)
Progress Energy [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service and interest costs - 1 Percentage Point Increase 1
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 9
Effect on total service and interest costs - 1 Percentage Point Decrease (1)
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (8)
Duke Energy Progress [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service and interest costs - 1 Percentage Point Increase 1
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 5
Effect on total service and interest costs - 1 Percentage Point Decrease (1)
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (5)
Duke Energy Florida [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 4
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (4)
Duke Energy Ohio [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 1
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (1)
Duke Energy Indiana [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 2
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease (2)
Piedmont Natural Gas [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Effect on post-retirement benefit obligation - 1 Percentage Point Increase 1
Effect on post-retirement benefit obligation - 1 Percentage Point Decrease $ (1)