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Risk Management Activities and Derivative Transactions Derivatives Under FTP (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Dec. 31, 2015 USD ($) | Sep. 30, 2015 USD ($)
Derivative |  |  |
FTP transaction limit |  | $ 130 |
Maximum hedge volume |  | 75.00% |
Market value limitation of outstanding construction materials hedging transactions |  | $ 100 |
Portfolio value at risk limit for foreign currency transactions |  | $ 5 |
Natural Gas |  |  |
Derivative |  |  |
Notional amount |  | 132,000,000 | 134,000,000
Fair value |  | $ (15) | $ 1
Number of Price Risk Derivatives Held |  | 30 | 33
Coal Contract |  |  |
Derivative |  |  |
Notional amount |  | 20,000,000 | 19,000,000
Fair value |  | $ (123) | $ (98)
Number of Price Risk Derivatives Held |  | 12 | 14
Swap contracts |  |  |
Derivative |  |  |
Remaining terms |  | 2 |
Natural Gas Swap |  |  |
Derivative |  |  |
Notional amount | [1] | 40,977,500 | 51,495,000
Fair value | [1] | $ (101) | $ (116)
Maximum | Natural Gas |  |  |
Derivative |  |  |
Derivative, Term of Contract |  | 3 years |
Maximum | Coal Contract |  |  |
Derivative |  |  |
Derivative, Term of Contract |  | 3 years |
[1] | Fair value amounts presented are based on the net commodity position with the counterparty. Notional amounts disclosed represent the net absolute value of contractual amounts.

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