Note 2 - Revenues from Contracts with Customers - Assets and Liabilities (Details) - USD ($) $ in Thousands |
6 Months Ended | ||
|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2025 |
|
| Accounts receivable, net | $ 30,640 | $ 28,666 | |
| Accounts payable | 989 | 1,159 | |
| Current portion of deferred revenue | 6,705 | 6,663 | |
| Deferred revenue | 59,744 | 58,067 | |
| Balance | 64,730 | $ 60,155 | |
| Increase due to minimums and lease amendment fees | 15,793 | 7,836 | |
| Recognition of previously deferred revenue | (14,074) | (12,049) | |
| Balance | 66,449 | $ 55,942 | |
| Coal Royalty Revenues [Member] | |||
| Accounts receivable, net | 26,228 | 24,372 | |
| Contract with customer, current | 0 | 84 | |
| Contract with customer, noncurrent | 7,353 | 5,281 | |
| Accounts payable | 125 | 211 | |
| Current portion of deferred revenue | 6,705 | 6,663 | |
| Deferred revenue | $ 59,744 | $ 58,067 | |
| X | ||||||||||
- Definition The amount of deferred revenue contractual minimum payments during the reporting period. No definition available.
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| X | ||||||||||
- Definition Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right to consideration is unconditional, classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right to consideration is unconditional, classified as noncurrent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable, classified as current. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable, classified as noncurrent. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Amount of revenue recognized that was previously reported as deferred or unearned revenue. No definition available.
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| X | ||||||||||
- Details
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