Employee Benefit Plans (Employee Savings Plans) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 49	$ 43
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	16	14
Progress Energy [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	14	12
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	11	9
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	4	4
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	1	1
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 2	$ 2