Fair Value Measurements (Additional Fair Value Disclosure) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 40,020	$ 40,256
Long-term debt, fair value	44,566	42,592
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	8,391	8,436
Long-term debt, fair value	9,626	9,123
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	14,754	14,115
Long-term debt, fair value	16,951	15,234
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	6,201	5,235
Long-term debt, fair value	6,696	5,323
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	4,860	4,886
Long-term debt, fair value	5,767	5,408
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,766	2,188
Long-term debt, fair value	1,970	2,237
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,791	3,796
Long-term debt, fair value	$ 4,456	$ 4,171