Employee Benefit Plans Employee Benefit Plans (Plan Contributions) (Details) - Pension Plan [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	$ 143
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	42
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	42
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	21
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	21
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	4
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by Employer	$ 9