Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Employee Savings Plans [Abstract]
Employer matching contributions	$ 34	$ 30	$ 120	$ 110
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Employer matching contributions	11	10	40	36
Progress Energy [Member]
Employee Savings Plans [Abstract]
Employer matching contributions	10	10	36	33
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Employer matching contributions	7	7	26	23
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Employer matching contributions	3	3	10	10
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Employer matching contributions			2	2
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Employer matching contributions	$ 1	$ 1	$ 5	$ 5