Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 14,092	$ 12,791
Heating Oil [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	885	300
Coal Contract [Member] | Coal Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	13,743	13,257
Coal Contract [Member] | Accrued expenses and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (536)	$ (766)