Investments in Debt and Equity Securities Investments in Debt and Equity Securities (Realized Gains and Losses)(Details) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	$ 31	$ 32	$ 62	$ 63
Realized losses	2	15	6	22
Duke Energy Carolinas [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	29	21	52	46
Realized losses	1	6	2	10
Progress Energy [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	2	10	9	15
Realized losses	1	7	3	9
Duke Energy Progress [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	1	6	7	8
Realized losses		3	2	4
Duke Energy Florida [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Realized gains	1	5	2	8
Realized losses		$ 3	$ 1	$ 4