Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Employee Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	$ 65	$ 52
Employee Savings Plan [Member] | Duke Energy Carolinas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	22	18
Employee Savings Plan [Member] | Progress Energy [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	18	15
Employee Savings Plan [Member] | Duke Energy Progress [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	13	11
Employee Savings Plan [Member] | Duke Energy Florida [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	5	4
Employee Savings Plan [Member] | Duke Energy Ohio [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	1	1
Employee Savings Plan [Member] | Duke Energy Indiana [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	3	2
Employee Savings Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contributions	2	$ 2
Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Contribution Plan Disclosure [Line Items]
Pension Contributions	$ 2