Employee Benefit Plans (Contributions to Defined Benefit Pension Plans) (Details) - Pension Plan [Member] - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		$ 141	$ 19	$ 155
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		46		43
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		45		43
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		25		24
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		20		20
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			4	5
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		$ 8		9
Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 10		$ 11		$ 10