Fair Value Measurements (Other Fair Value Disclosures) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	$ 59,863	$ 58,126
Long-term debt, fair value	69,292	63,062
Unamortized debt discount and premium, net	1,300	1,500
Duke Energy Carolinas
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	12,218	11,900
Long-term debt, fair value	14,917	13,516
Progress Energy
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	19,264	19,634
Long-term debt, fair value	23,470	22,291
Duke Energy Progress
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	9,258	9,058
Long-term debt, fair value	10,862	9,934
Duke Energy Florida
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	7,915	7,987
Long-term debt, fair value	9,756	9,131
Duke Energy Ohio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	3,089	2,619
Long-term debt, fair value	3,650	2,964
Duke Energy Indiana
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	4,091	4,057
Long-term debt, fair value	5,204	4,800
Piedmont
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	2,780	2,384
Long-term debt, fair value	$ 3,306	$ 2,642