Employee Benefit Plans (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Remeasurement gain recognized	$ 18
Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.50%
Cash balance interest crediting rate	4.00%
Increase in plan assets	$ 275
Increase in projected benefit obligation	257
Settlement charge	69
Duke Energy Carolinas [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	43
Duke Energy Progress [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	16
Duke Energy Florida [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	3
Duke Energy Indiana [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	3
Duke Energy Ohio [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	1
Piedmont Natural Gas [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	$ 3