Concentrations of Credit Risk (Details) (Customer Concentration Risk [Member])	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	462812	452530
Accounts Receivable [Member] | Steam Coal Utilities [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	210164	220052
Accounts Receivable [Member] | Steel and Coke Producers [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	93303	69470
Accounts Receivable [Member] | Coal Brokers and Distributors [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	38033	54996
Accounts Receivable [Member] | Gas Customers [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	63299	65358
Accounts Receivable [Member] | All Other [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	58013	42654
Sales Revenue, Goods, Net [Member] | XCoal Energy and Resources [Member]
Concentration Risk [Line Items]
Concentration Risk, Customer	662109