Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 30	$ 19	$ 71	$ 47
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	10	9	24	20
Progress Energy [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	10	10	22	22
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	6	6	12	12
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	$ 1	$ 1	$ 3	$ 3