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Fair Value Measurements (Details 5) - USD ($) $ in Millions | Dec. 31, 2016 | Dec. 31, 2015
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Carrying Value |  |
Fair value and related carrying amounts of long-term debt and other long-term obligations |  |
Long-term debt and other long-term obligations | $ 19,885 | $ 20,244
Fair Value |  |
Fair value and related carrying amounts of long-term debt and other long-term obligations |  |
Long-term debt and other long-term obligations | 19,829 | 21,519
FES | Carrying Value |  |
Fair value and related carrying amounts of long-term debt and other long-term obligations |  |
Long-term debt and other long-term obligations | 3,000 | 3,027
FES | Fair Value |  |
Fair value and related carrying amounts of long-term debt and other long-term obligations |  |
Long-term debt and other long-term obligations | $ 1,555 | $ 3,121

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