Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 15,151	$ 19,942
Heating Oil [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	2,835	5,103
Coal Contract [Member] | Coal Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	12,316	14,851
Coal Contract [Member] | Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 0	$ (12)