Inventory Components (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Inventory [Line Items]
Coal	$ 105,378	$ 108,694
Merchandise for resale	43,639	50,120
Supplies	109,318	99,724
Total Inventories	258,335	258,538
Excess of replacement cost of merchandise for resl inventories over carrying LIFO value	$ 22,406	$ 19,624