Fair Value Measurements (Additional Fair Value Disclosure) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 39,169	$ 40,020
Long-term debt, fair value	42,276	44,566
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	8,885	8,391
Long-term debt, fair value	9,695	9,626
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	14,206	14,754
Long-term debt, fair value	15,689	16,951
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	5,657	6,201
Long-term debt, fair value	5,881	6,696
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	4,855	4,860
Long-term debt, fair value	5,507	5,767
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,605	1,766
Long-term debt, fair value	1,760	1,970
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,791	3,791
Long-term debt, fair value	$ 4,259	$ 4,456