Note 12 - Long-term Debt - Long-term Debt (Details) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Principal Amount	$ 652,555	$ 696,178
Unamortized discount	$ 11,478	$ 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	10.78%	10.78%
Loans Payable [Member] | Term Loan B Facility [Member]
Principal Amount	$ 271,563	$ 272,938
Unamortized discount	$ 1,062	$ 1,187
Debt, Weighted Average Interest Rate	4.68%	6.30%
Senior Notes [Member] | Senior Secured Second Lien Notes due 2025 [Member]
Debt, Weighted Average Interest Rate	11.00%	11.00%