Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Savings Plans [Abstract]
Matching contribution percentage	100.00%
Eligible pay percentage	6.00%
Additional contribution percentage for employees not participating in defined pension plans	4.00%
Employer contributions	$ 214	$ 213	$ 179
Duke Energy Carolinas
Employee Savings Plans [Abstract]
Employer contributions	66	68	61
Progress Energy
Employee Savings Plans [Abstract]
Employer contributions	58	58	53
Duke Energy Progress
Employee Savings Plans [Abstract]
Employer contributions	38	40	37
Duke Energy Florida
Employee Savings Plans [Abstract]
Employer contributions	20	19	16
Duke Energy Ohio
Employee Savings Plans [Abstract]
Employer contributions	5	4	3
Duke Energy Indiana
Employee Savings Plans [Abstract]
Employer contributions	11	10	9
Piedmont
Employee Savings Plans [Abstract]
Employer contributions	$ 13	$ 12	$ 7
Minimum | Piedmont
Employee Savings Plans [Abstract]
Additional contribution percentage for employees not participating in defined pension plans	3.00%
Maximum | Piedmont
Employee Savings Plans [Abstract]
Additional contribution percentage for employees not participating in defined pension plans	5.00%