Fair Value Measurements (Other Fair Value Disclosures) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	$ 58,126	$ 54,529
Long-term debt, fair value	63,062	54,534
Unamortized debt discount and premium, net	1,500	1,600
Duke Energy Carolinas
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	11,900	10,939
Long-term debt, fair value	13,516	11,471
Progress Energy
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	19,634	18,911
Long-term debt, fair value	22,291	19,885
Duke Energy Progress
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	9,058	8,204
Long-term debt, fair value	9,934	8,300
Duke Energy Florida
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	7,987	7,321
Long-term debt, fair value	9,131	7,742
Duke Energy Ohio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	2,619	2,165
Long-term debt, fair value	2,964	2,239
Duke Energy Indiana
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	4,057	3,782
Long-term debt, fair value	4,800	4,158
Piedmont
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	2,384	2,138
Long-term debt, fair value	$ 2,642	$ 2,180