Commitments and Contingencies (Schedule of Reserves) (Details) - Loss Contingency, Nature [Domain] - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Reserves for legal matters	$ 191	$ 323
Duke Energy Carolinas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	19	72
Progress Energy [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	79	93
Duke Energy Progress [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	22	37
Duke Energy Florida [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	36	$ 36
Duke Energy Ohio [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	$ 81