Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 47,165	$ 39,569
Long-term debt, fair value	50,997	42,537
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	9,360	8,367
Long-term debt, fair value	10,799	9,156
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	16,520	14,464
Long-term debt, fair value	19,060	15,856
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	7,011	6,518
Long-term debt, fair value	7,787	6,757
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	6,128	4,266
Long-term debt, fair value	7,127	4,908
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	1,887	1,598
Long-term debt, fair value	2,128	1,724
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	3,787	3,768
Long-term debt, fair value	$ 4,538	$ 4,219