Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 72,405	$ 65,323
Taxes other than income taxes	121,029	133,331
Interest	42,413	55,266
Coal supply agreement liability	14,038	38,441
Workers’ compensation	10,371	11,666
Asset retirement obligations	38,920	27,119
Other	18,842	17,061
Accrued Liabilities, Current	$ 318,018	$ 348,207