Derivatives And Hedging (Schedule Of Outstanding Derivative Instruments) (Details) - MMBTU	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Natural Gas [Member]
Derivative [Line Items]
Quantity	14,250,000	10,620,000

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.

No definition available.

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Period Type:	duration