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DERIVATIVE INSTRUMENTS - VOLUME (Details) certificate in Thousands, $ in Millions | Sep. 30, 2017 USD ($) Bcf certificate | Sep. 30, 2016 Bcf | Jun. 01, 2015 USD ($)
--- | --- | --- | ---
Derivative [Line Items] |  |  |
Derivative, notional amount | $ |  |  | $ 125.0
Foreign currency contracts |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | $ | $ 4.5 |  |
Energy Services | Physical commodity contracts |  |  |
Derivative [Line Items] |  |  |
Number of Solar Renewable Energy Certificates (in certificates) | certificate | 283 |  |
Long | Natural Gas Distribution | Futures |  |  |
Derivative [Line Items] |  |  |
Outstanding long (short) derivatives (in Bcf) | 18.2 | 23.6 |
Long | Natural Gas Distribution | Physical |  |  |
Derivative [Line Items] |  |  |
Outstanding long (short) derivatives (in Bcf) | 32.1 | 9.2 |
Long | Energy Services | Physical |  |  |
Derivative [Line Items] |  |  |
Outstanding long (short) derivatives (in Bcf) |  | 94.6 |
Long | Energy Services | Financial Options |  |  |
Derivative [Line Items] |  |  |
Outstanding long (short) derivatives (in Bcf) | 0.0 | 1.2 |
Short | Energy Services | Futures |  |  |
Derivative [Line Items] |  |  |
Outstanding long (short) derivatives (in Bcf) | 16.4 | 79.1 |
Short | Energy Services | Physical |  |  |
Derivative [Line Items] |  |  |
Outstanding long (short) derivatives (in Bcf) | 13.1 |  |

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