Fair Value Measurements (Additional Fair Value Disclosure) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 43,188	$ 42,592
Long-term debt	39,885	40,256
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	9,346	9,123
Long-term debt	8,436	8,436
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	16,083	15,234
Long-term debt	15,046	14,115
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	5,940	5,323
Long-term debt	5,717	5,235
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	5,783	5,408
Long-term debt	5,110	4,886
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	2,299	2,237
Long-term debt	2,187	2,188
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	4,279	4,171
Long-term debt	$ 3,796	$ 3,796