Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Reserves for legal matters	$ 181	$ 166
Duke Energy Carolinas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	11	11
Progress Energy [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	54	54
Duke Energy Progress [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	6	6
Duke Energy Florida [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	31	31
Duke Energy Ohio [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	$ 80	$ 80