Other Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Other Liabilities Disclosure [Abstract]
Subsidence Liability	$ 98,573	$ 88,939
Accrued Salaries, Current	38,953	39,172
Interest Payable, Current	63,600	63,687
Accrual for Taxes Other than Income Taxes, Current	26,305	35,943
Accrued Bonuses, Current	30,371	28,744
Liability for Uncertain Tax Positions, Current	28,530	2,100
Other Accrued Liabilities, Current	122,902	144,352
Other Postretirement Benefits Payable	60,847	58,452
Accrued Reclamation Costs, Current	9,552	20,582
Pneumoconiosis Liability, Current	9,212	8,838
Defined Benefit Pension Plan Liabilities, Current	4,593	6,937
Long Term Disability, Current	4,340	4,016
Mine closing liability, current	13,628	9,176
Gas well closing liability, current	23,971	9,729
Workers' Compensation Liability, Current	$ 30,320	$ 25,081