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Fair Value Measurements (Details 5) - USD ($) $ in Millions | Mar. 31, 2017 | Dec. 31, 2016
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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 | $ 19,921 | $ 19,885
Carrying Value | FES |  |
Fair value and related carrying amounts of long-term debt and other long-term obligations |  |
Long-term debt and other long-term obligations | 2,971 | 3,000
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 | 20,029 | 19,829
Fair Value | FES |  |
Fair value and related carrying amounts of long-term debt and other long-term obligations |  |
Long-term debt and other long-term obligations | $ 1,424 | $ 1,555

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