Leases (Rent Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Leased Assets [Line Items]
Rental expense on operating leases	$ 268	$ 241
Duke Energy Carolinas
Operating Leased Assets [Line Items]
Rental expense on operating leases	49	44
Progress Energy
Operating Leased Assets [Line Items]
Rental expense on operating leases	143	130
Duke Energy Progress
Operating Leased Assets [Line Items]
Rental expense on operating leases	75	75
Duke Energy Florida
Operating Leased Assets [Line Items]
Rental expense on operating leases	68	55
Duke Energy Ohio
Operating Leased Assets [Line Items]
Rental expense on operating leases	13	15
Duke Energy Indiana
Operating Leased Assets [Line Items]
Rental expense on operating leases	21	23
Piedmont
Operating Leased Assets [Line Items]
Rental expense on operating leases	$ 11	$ 7