Note 13 - Debt - Long-term Debt (Details) (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Principal Amount	$ 611,448
Unamortized discount	$ 9,921	$ 10,323
MEDCO Revenue Bonds in Series Due September 2025 at 5.75% [Member]
Debt, Weighted Average Interest Rate	5.75%	5.75%
Term Loan A Facility [Member]
Debt, Weighted Average Interest Rate	5.50%	5.55%
Advance Royalty Commitments [Member]
Debt, Weighted Average Interest Rate	13.68%	10.78%
Loans Payable [Member] \| Term Loan B Facility [Member]
Principal Amount	$ 270,188	$ 272,938
Unamortized discount	$ 938	$ 1,187
Debt, Weighted Average Interest Rate	4.65%	6.30%
Senior Notes [Member] \| Senior Secured Second Lien Notes due 2025 [Member]
Debt, Weighted Average Interest Rate	11.00%	11.00%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant