Fair Value Measurements (Other Fair Value Disclosure) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 60,718	$ 58,126
Long-term debt, fair value	69,503	63,062
Piedmont Natural Gas and Progress Energy
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized debt discount (premium), net	1,400	1,500
Duke Energy Carolinas
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	12,548	11,900
Long-term debt, fair value	15,165	13,516
Progress Energy
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	19,865	19,634
Long-term debt, fair value	23,825	22,291
Duke Energy Progress
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	9,358	9,058
Long-term debt, fair value	10,808	9,934
Duke Energy Florida
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,917	7,987
Long-term debt, fair value	9,684	9,131
Duke Energy Ohio
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	3,089	2,619
Long-term debt, fair value	3,619	2,964
Duke Energy Indiana
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	4,104	4,057
Long-term debt, fair value	5,140	4,800
Piedmont Natural Gas
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,780	2,384
Long-term debt, fair value	$ 3,276	$ 2,642