Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 49,515	$ 47,895
Long-term debt, fair value	51,947	49,161
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	9,524	9,603
Long-term debt, fair value	10,657	10,494
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	18,145	17,541
Long-term debt, fair value	20,101	19,107
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	6,760	7,011
Long-term debt, fair value	7,266	7,357
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	6,979	6,125
Long-term debt, fair value	7,753	6,728
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	1,977	1,884
Long-term debt, fair value	2,155	2,020
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	3,784	3,786
Long-term debt, fair value	4,379	4,260
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	1,946	1,821
Long-term debt, fair value	$ 2,107	$ 1,933