Details Of Certain Accounts - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related benefits	$ 26,443	$ 24,768
Accrued interest	2,760	7,098
Income tax payable	581
Deferred revenue	9,425	8,140
Asset retirement obligations	29,018	30,913
Other	17,013	16,116
Total accrued liabilities	$ 85,240	$ 87,035

Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all currently due domestic and foreign income tax obligations.

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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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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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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. 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 [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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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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