Employee Benefit Plans (Plan Contributions) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	$ 141	$ 8
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	46
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	45
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	25
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	20
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	$ 8
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer		$ 4