Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 68,245	$ 72,405
Taxes other than income taxes	113,872	121,029
Interest	80,454	42,413
Acquired sales contracts	14,461	14,038
Workers’ compensation	12,215	10,371
Asset retirement obligations	38,895	38,920
Other	20,891	18,842
Accrued Liabilities, Current	$ 349,033	$ 318,018