Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 42,273	$ 39,569
Long-term debt, fair value	47,953	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	10,874	9,156
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	15,486	14,464
Long-term debt, fair value	16,715	15,856
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	6,565	6,518
Long-term debt, fair value	7,344	6,757
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	5,540	4,266
Long-term debt, fair value	5,226	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	2,134	1,724
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,937	3,768
Long-term debt, fair value	$ 4,717	$ 4,219