Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer				$ 8
Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer				4
Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer					$ 1
Employee Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		$ 43	$ 39	147	130
Employee Savings Plan [Member] | Duke Energy Carolinas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		14	13	49	44
Employee Savings Plan [Member] | Progress Energy [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		12	12	42	39
Employee Savings Plan [Member] | Duke Energy Progress [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		9	8	30	27
Employee Savings Plan [Member] | Duke Energy Florida [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		4	3	13	11
Employee Savings Plan [Member] | Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		1	1	3	3
Employee Savings Plan [Member] | Duke Energy Indiana [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		2	2	7	6
Employee Savings Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		$ 2	$ 2	$ 5	$ 5
Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions by Employer	$ 2