Derivative Instruments (Schedule of Natural Gas Derivative Positions) (Details) - Natural Gas	Jun. 30, 2018 MMBTU / d $ / MMBTU
Q3 - Q4 2018 \| Fixed Price Swaps
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| MMBTU / d	25,000
Weighted Average Fixed Price ($/MMBtu) \| $ / MMBTU	3.01
Q3 - Q4 2018 \| Call Option
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| MMBTU / d	33,000
Weighted Average Ceiling Price ($/MMBtu) \| $ / MMBTU	3.25
FY 2019 \| Call Option
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| MMBTU / d	33,000
Weighted Average Ceiling Price ($/MMBtu) \| $ / MMBTU	3.25
FY 2020 \| Call Option
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| MMBTU / d	33,000
Weighted Average Ceiling Price ($/MMBtu) \| $ / MMBTU	3.50

- Definition

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

The average cap rate on a group of price risk derivatives such as caps or collars. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

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