Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 5,798	$ 9,052
Accrued expenses and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	(355)	0
Heating Oil and Foreign Currency [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	3,973	1,017
Coal and Natural Gas Contracts [Member] | Coal Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 2,180	$ 8,035