Fair Value Measurements (Other Fair Value Disclosure) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 57,914	$ 54,529
Long-term debt, fair value	63,276	54,534
Piedmont Natural Gas and Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized debt discount (premium), net	1,500	1,600
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	11,758	10,939
Long-term debt, fair value	13,462	11,471
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	19,119	18,911
Long-term debt, fair value	21,952	19,885
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	9,049	8,204
Long-term debt, fair value	9,995	8,300
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,132	7,321
Long-term debt, fair value	8,356	7,742
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,719	2,165
Long-term debt, fair value	3,096	2,239
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	4,208	3,782
Long-term debt, fair value	5,018	4,158
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,384	2,138
Long-term debt, fair value	$ 2,664	$ 2,180