Fair Value Measurements (Other Fair Value Disclosure) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	$ 61,388	$ 58,126
Long-term debt, fair value	65,644	63,062
Piedmont Natural Gas and Progress Energy [Member]
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	12,807	11,900
Long-term debt, fair value	14,312	13,516
Progress Energy
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	19,355	19,634
Long-term debt, fair value	21,802	22,291
Duke Energy Progress
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	9,059	9,058
Long-term debt, fair value	9,798	9,934
Duke Energy Florida
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	7,706	7,987
Long-term debt, fair value	8,831	9,131
Duke Energy Ohio
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,620	2,619
Long-term debt, fair value	2,904	2,964
Duke Energy Indiana
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	4,603	4,057
Long-term debt, fair value	5,433	4,800
Piedmont Natural Gas
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, book value	2,385	2,384
Long-term debt, fair value	$ 2,551	$ 2,642