Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Remeasurement gain (loss) recognized		$ 18
Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.20%	3.50%
Cash balance interest crediting rate	4.00%	4.00%
Remeasurement gain (loss) recognized	$ 136
Increase (decrease) in plan assets	10	$ 275
Increase in projected benefit obligation	126	257
Settlement charge	16	69
Duke Energy Carolinas [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	6	43
Duke Energy Progress [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	3	16
Duke Energy Florida [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	2	3
Duke Energy Indiana [Member] | Duke Energy RCBP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	1	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	$ 3