Other Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
OTHER ACCRUED LIABILITIES [Abstract]
subsidence liability	$ 108,094	$ 83,751
Accrued Salaries, Current	65,775	58,771
Interest Payable, Current	63,577	64,695
Accrual for Taxes Other than Income Taxes, Current	50,869	56,839
Accrued Bonuses, Current	37,947	38,474
Liability for Uncertain Tax Positions, Current	6,820	41,235
Other Accrued Liabilities, Current	128,247	139,079
Other Postretirement Benefits Payable	182,529	179,809
Mine closing liability, current	34,501	38,433
Workers' Compensation Liability, Current	24,837	27,754
Gas well closing liability, current	24,660	27,919
Accrued Reclamation Costs, Current	20,180	25,933
pneumoconiosis liability, current	10,027	10,915
long term disability, current	6,294	6,126
Defined Benefit Pension Plan Liabilities, Current	5,713	2,258
Accrued Liabilities, Current	$ 770,070	$ 801,991