Employee Benefit Plans (Contributions to Defined Benefit Pension Plans) (Details) - Pension Plan [Member] - USD ($) $ in Millions		2 Months Ended	12 Months Ended
	Jan. 02, 2018	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			$ 148
Employer contributions			19	$ 155		$ 302
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			46
Employer contributions				43		91
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			45
Employer contributions				43		83
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			25
Employer contributions				24		42
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			20
Employer contributions				20		40
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			4	5		8
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			8
Employer contributions				9		19
Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contribution			7
Employer contributions		$ 10	$ 11		$ 10		$ 10
Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 141
Anticipated contributions remainder of 2018	7
Subsequent Event [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	46
Subsequent Event [Member] | Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	45
Subsequent Event [Member] | Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	25
Subsequent Event [Member] | Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	20
Subsequent Event [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	8
Subsequent Event [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated contributions remainder of 2018	$ 7