Commitments and Contingencies (Schedule of Reserves) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Reserves for legal matters	$ 331	$ 323
Duke Energy Carolinas [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	72	72
Progress Energy [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	93	93
Duke Energy Progress [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	37	37
Duke Energy Florida [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	34	36
Duke Energy Ohio [Member]
Loss Contingencies [Line Items]
Reserves for legal matters	$ 10