Investments in Debt and Equity Securities (Realized Gains and Losses)(Details) (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
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	$ 28	$ 72	$ 90	$ 135
Realized losses	51	16	57	38
Duke Energy Carolinas [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	20	49	72	95
Realized losses	48	1	50	11
Progress Energy [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	8	22	17	37
Realized losses	3	11	6	20
Duke Energy Progress [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	4	7	11	15
Realized losses	2	2	4	6
Duke Energy Florida [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	3	14	5	22
Realized losses	$ 1	$ 9	$ 2	$ 13