Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Employee Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		$ 39	$ 39	$ 104	$ 91
Employee Savings Plan [Member] | Duke Energy Carolinas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		13	13	35	31
Employee Savings Plan [Member] | Progress Energy [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		12	12	30	27
Employee Savings Plan [Member] | Duke Energy Progress [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		8	8	21	19
Employee Savings Plan [Member] | Duke Energy Florida [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		4	4	9	8
Employee Savings Plan [Member] | Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		1	1	2	2
Employee Savings Plan [Member] | Duke Energy Indiana [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		2	2	5	4
Employee Savings Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions		$ 1	$ 1	$ 3	$ 3
Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Payment for Pension Benefits	$ 2