Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Royalties	$ 50,831	$ 74,061
Accrued Interest	25,304	30,862
Transportation Charges	22,353	16,533
Accrued Other Taxes	11,660	9,115
Accrued Payroll & Benefits	6,608	6,248
Short-Term Incentive Compensation	5,178	21,030
Deferred Revenue	3,423	13,964
Other	30,755	37,610
Current Portion of Long-Term Liabilities:
Asset Retirement Obligations	5,076	5,076
Salary Retirement	1,629	1,587
Total Other Accrued Liabilities	$ 162,817	$ 216,086

Accrued Transportation Charges

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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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Amount of expenses incurred but not yet paid nor invoiced, and liabilities classified as other.

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Carrying value as of the balance sheet date of obligations incurred through that date and payable for royalties.

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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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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

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Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as current. Excludes other postretirement benefit plan.

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Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits.

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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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