Other Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Other Liabilities Disclosure [Abstract]
Subsidence Liability	$ 103,343	$ 98,573
Accrued Royalties	52,456	34,110
Interest Payable, Current	51,404	63,600
Accrual for Taxes Other than Income Taxes, Current	17,951	26,305
Taxes, Other	0	28,530
Accrued Bonuses, Current	49,533	0
Liability for Uncertain Tax Positions, Current	37,293	38,953
Accrued Bonuses	36,272	30,371
Other Accrued Liabilities, Current	100,284	87,407
Other Postretirement Benefits Payable	57,279	60,847
Accrued Reclamation Costs, Current	9,339	4,593
Pneumoconiosis Liability, Current	9,156	9,211
Defined Benefit Pension Plan Liabilities, Current	6,075	9,552
Long Term Disability, Current	3,957	4,340
Mine closing liability, current	15,122	15,014
Gas well closing liability, current	21,286	23,971
Workers' Compensation Liability, Current	32,222	30,320
Other Accrued Liabilities	$ 602,972	$ 565,697