v3.3.0.814

Investments in Debt and Equity Securities (Realized Gains and Losses)(Details) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract] |  |  |  |
Realized gains | $ 30 | $ 28 | $ 160 | $ 90
Realized losses | 28 | 51 | 59 | 57
Duke Energy Carolinas [Member] |  |  |  |
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract] |  |  |  |
Realized gains | 25 | 20 | 132 | 72
Realized losses | 24 | 48 | 47 | 50
Progress Energy [Member] |  |  |  |
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract] |  |  |  |
Realized gains | 5 | 8 | 26 | 17
Realized losses | 4 | 3 | 10 | 6
Duke Energy Progress [Member] |  |  |  |
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract] |  |  |  |
Realized gains | 4 | 4 | 21 | 11
Realized losses | 3 | 2 | 8 | 4
Duke Energy Florida [Member] |  |  |  |
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract] |  |  |  |
Realized gains | 1 | 3 | 5 | 5
Realized losses | $ 1 | $ 1 | $ 2 | $ 2

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