Derivatives (Effects Of Derivatives On Measures Of Financial Performance) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ 74	$ (358)
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	302	859
Not Designated as Hedging Instrument [Member] | Coal Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(1,302)	1,470
Coal derivative settlements, non-hedging	2,879	9,217
Not Designated as Hedging Instrument [Member] | Heating Oil-Fuel Surcharges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(254)	(565)
Not Designated as Hedging Instrument [Member] | Heating Oil-Diesel Purchases [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(2,963)	(4,261)
Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	8	0
Coal sales [Member] | Coal Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	(515)	(176)
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	706	1,221
Coal purchases [Member] | Coal Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	589	(182)
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	$ (404)	$ (362)