OTHER ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Subsidence Liability	$ 90,923	$ 83,532
Accrued Payroll and Benefits	21,138	12,978
Accrued Interest	6,746	6,850
Accrued Other Taxes	3,931	5,050
Litigation	2,935	8,235
Short-Term Incentive Compensation	1,935	6,024
Other	10,364	15,588
Current Portion of Long-Term Liabilities:
Postretirement Benefits Other than Pensions	32,356	32,345
Asset Retirement Obligations	29,413	31,017
Operating Lease Liability	15,798
Workers' Compensation	12,227	12,628
Pneumoconiosis Benefits	11,253	12,187
Total Other Accrued Liabilities	$ 239,019	$ 226,434

Accrued Payroll And Employee Benefits, Current

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Accrued Subsidence Liability, Current

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Employee Related Liabilities, Medical And Disability Benefits, Current

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Liability, Other Postretirement Defined Benefit Plan, Current

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Long-Term Liabilities, Current [Abstract]

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Carrying value as of the balance sheet date of obligations incurred and payable for real and property taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying value as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to employees and directors or earned by them based on the terms of one or more relevant arrangements. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying amount of reserve for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs, which is expected to be paid within one year of the date of the statement of financial position.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer.

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Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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