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DERIVATIVE INSTRUMENTS - VOLUME (Details) certificate in Thousands | Mar. 31, 2018 USD ($) Bcf certificate | Sep. 30, 2017 Bcf | Jun. 01, 2015 USD ($)
--- | --- | --- | ---
Derivative [Line Items] |  |  |
Derivative, notional amount | $ |  |  | $ 125,000,000
Foreign currency contracts |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | $ | $ 8,800,000 |  |
Natural Gas Distribution | Long | Futures |  |  |
Derivative [Line Items] |  |  |
Outsanding long (short) derivatives, Volume | 24.9 | 18.2 |
Natural Gas Distribution | Long | Physical |  |  |
Derivative [Line Items] |  |  |
Outsanding long (short) derivatives, Volume | 33.2 | 32.1 |
Energy Services | Physical commodity contracts |  |  |
Derivative [Line Items] |  |  |
Number of SRECs | certificate | 567 |  |
Energy Services | Short | Futures |  |  |
Derivative [Line Items] |  |  |
Outsanding long (short) derivatives, Volume | (13.0) | (16.4) |
Energy Services | Short | Physical |  |  |
Derivative [Line Items] |  |  |
Outsanding long (short) derivatives, Volume | 36.5 | (13.1) |

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