Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 65	$ 88
Duke Energy Carolinas [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	9	30
Progress Energy [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	54	55
Duke Energy Progress [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	12	13
Duke Energy Florida [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	24	24
Piedmont Natural Gas [Member]
Legal Reserves Details [Line Items]
Reserves for legal matters	$ 1	$ 2