Employee Benefit Plans (Contributions to Defined Benefit Pension Plans) (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0	$ 77	$ 141
Duke Energy Carolinas
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0	7	46
Progress Energy
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0	57	45
Duke Energy Progress
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0	4	25
Duke Energy Florida
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0	53	20
Duke Energy Ohio
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0	2	0
Duke Energy Indiana
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0	2	8
Piedmont
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0	$ 1	$ 0