Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 166	$ 323
Duke Energy Carolinas [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	11	72
Progress Energy [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	54	93
Duke Energy Progress [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	6	37
Duke Energy Florida [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	31	$ 36
Duke Energy Ohio [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 80