v2.4.0.8

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

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