Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	$ 41	$ 28
Duke Energy Carolinas [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	14	11
Progress Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	12	12
Duke Energy Progress [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	6	6
Duke Energy Florida [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	4	4
Duke Energy Ohio [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	1	1
Duke Energy Indiana [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan contribution by employer	$ 2	$ 2