Fair Value Measurements (Additional Fair Value Disclosure) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 39,858	$ 40,256
Long-term debt, fair value	43,602	42,592
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	8,394	8,436
Long-term debt, fair value	9,426	9,123
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	14,512	14,115
Long-term debt, fair value	16,305	15,234
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	5,716	5,235
Long-term debt, fair value	6,013	5,323
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	5,102	4,886
Long-term debt, fair value	5,867	5,408
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,783	2,188
Long-term debt, fair value	1,967	2,237
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,795	3,796
Long-term debt, fair value	$ 4,356	$ 4,171