Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 58,220	$ 67,621
Taxes other than income taxes	112,406	114,664
Interest	79,731	18,528
Acquired sales contracts	14,439	14,373
Workers’ compensation	16,470	12,434
Asset retirement obligations	22,682	24,940
Other	24,613	26,027
Accrued Liabilities, Current	$ 328,561	$ 278,587