Investments in Debt and Equity Securities (Realized Gains and Losses)(Details) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	$ 28	$ 31	$ 130	$ 62
Realized losses	17	2	31	6
Duke Energy Carolinas [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	17	29	107	52
Realized losses	11	1	23	2
Progress Energy [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	9	2	21	9
Realized losses	5	1	6	3
Duke Energy Progress [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	8	1	17	7
Realized losses	4		5	2
Duke Energy Florida [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	1	$ 1	4	2
Realized losses	$ 1		$ 1	$ 1