Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 62,890	$ 72,405
Taxes other than income taxes	119,018	121,029
Interest	40,150	42,413
Coal supply agreement liability	15,550	14,038
Workers’ compensation	14,033	10,371
Asset retirement obligations	38,919	38,920
Other	16,529	18,842
Accrued Liabilities, Current	$ 307,089	$ 318,018