Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 37	$ 36	$ 86	$ 80
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	13	12	29	26
Progress Energy [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	12	11	26	23
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	8	7	19	16
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	3	3	7	7
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	1	1	2	2
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 2	$ 2	$ 4	$ 4