Employee Benefit Plans (Contributions to Defined Benefit Pension Plans) (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 77	$ 141	$ 19
Duke Energy Carolinas
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	7	46	0
Progress Energy
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	57	45	0
Duke Energy Progress
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	4	25	0
Duke Energy Florida
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	53	20	0
Duke Energy Ohio
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	2	0	4
Duke Energy Indiana
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	2	8	0
Piedmont
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 1	$ 0	$ 11