Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 8,204	$ 9,052
Heating Oil [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	4,589	1,017
Coal Contract [Member] | Coal Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	4,091	8,035
Coal Contract [Member] | Accrued expenses and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (476)	$ 0