Derivatives (Effects Of Derivatives On Measures Of Financial Performance) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ 2,190	$ 81	$ 1,797	[1]	$ 3,861	[1]
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	788	542	2,189	[1]	1,552	[1]
Coal Purchases [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	(942)	(178)	(511)	[1]	(1,122)	[1]
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	(123)		(633)	[1]		[1]
Coal Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	3,132	259	2,308	[2]	4,983	[2]
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	911	542	2,822	[2]	1,552	[2]
Coal [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(10,668)	(11,328)	(5,089)	[3]	23,670	[3]
Coal derivative settlements, non-hedging	9,929	14,072	25,725	[4]	25,901	[4]
Heating Oil-Diesel Purchases [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(288)	5,184	(9,760)	[4]	(16,902)	[4]
Heating Oil-Fuel Surchages [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	$ (222)	$ 1,092	$ (817)	[4]	$ (1,140)	[4]

[1] Cost of sales

[2] Revenues

[3] Change in fair value of coal derivatives and coal trading activities, net

[4] Other operating income, net