Employee Benefit Plans (Employee Savings Plans) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 30	[1]	$ 30	$ 110	[1]	$ 101
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	10	[1]	10	36	[1]	34
Progress Energy [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	10	[1]	12	33	[1]	34
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	7	[1]	7	23	[1]	19
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	3	[1]	4	10	[1]	11
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions		[1]		2	[1]	2
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Pretax employer matching contributions	$ 1	[1]	$ 2	$ 5	[1]	$ 5

[1] For the three and nine months ended September 30, 2014, amounts include the additional contribution of 4 percent of eligible pay per pay period for employees not eligible to participate in a defined benefit plan.