Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Payroll and employee benefits	$ 52,305	$ 73,362
Taxes other than income taxes	111,208	114,598
Interest	77,423	30,384
Acquired sales contracts	4,946	12,453
Workers’ compensation	17,635	16,714
Asset retirement obligations	19,199	19,222
Other	28,031	35,663
Accrued Liabilities, Current	$ 310,747	$ 302,396