Fair Value Measurements (Other Fair Value Disclosure) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 57,040	$ 54,529
Long-term debt, fair value	60,667	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	10,964	10,939
Long-term debt, fair value	12,300	11,471
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	19,199	18,911
Long-term debt, fair value	21,408	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	9,707	8,300
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,213	7,321
Long-term debt, fair value	8,173	7,742
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,509	2,165
Long-term debt, fair value	2,779	2,239
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	3,723	3,782
Long-term debt, fair value	4,363	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	$ 2,576	$ 2,180