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Derivative Instruments (Fair Values of Derivative Instruments in Consolidated Balance Sheets) (Details) - Not Designated as Hedging Instrument [Member] - Commodity Forward Contracts [Member] | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 MMBTU gal | Dec. 31, 2016 MMBTU gal
Derivatives, Fair Value [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | gal | 221,800,000 | 257,000,000
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 8,800,000 | 8,500,000

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- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Definition Nominal volume used to calculate payments on a derivative instrument. + 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. + Details
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- Details
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- Details
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Balance Type: |
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