Accrued Expenses and Other Current Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Payroll and employee benefits	$ 72,116	$ 67,621
Taxes other than income taxes	114,183	114,664
Interest	77,564	18,528
Acquired sales contracts	12,690	14,373
Workers’ compensation	16,085	12,434
Asset retirement obligations	22,681	24,940
Other	27,390	26,027
Accrued Liabilities, Current	$ 342,709	$ 278,587