Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 63,375	$ 72,405
Taxes other than income taxes	121,159	121,029
Interest	83,855	42,413
Coal supply agreement liability	14,456	14,038
Workers’ compensation	12,732	10,371
Asset retirement obligations	38,919	38,920
Other	17,544	18,842
Accrued Liabilities, Current	$ 352,040	$ 318,018