Note 13 - Long-term Debt - Long-term Debt (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Long-term Debt, Total		$ 625,348	$ 600,589
Unamortized discount		9,853	9,921
Long-term Debt, Current Maturities, Total	[1]	27,651	33,731
Long-Term Debt		597,697	566,858
MEDCO Revenue Bonds in Series Due September 2025 at 5.75% [Member]
Long-term Debt, Total		102,865	102,865
PEDFA Solid Waste Disposal Revenue Bonds [Member]
Long-term Debt, Total		75,000	0
Term Loan A Facility [Member]
Long-term Debt, Total		41,250	66,250
Other Asset Backed Financing [Member]
Long-term Debt, Total		2,267	2,813
Advance Royalty Commitments [Member]
Long-term Debt, Total		2,185	2,185
Loans Payable [Member] | Term Loan B Facility [Member]
Long-term Debt, Total		262,527	269,250
Unamortized discount		750	938
Senior Notes [Member] | Senior Secured Second Lien Notes due 2025 [Member]
Long-term Debt, Total		$ 149,107	$ 167,147

[1] Excludes current portion of Finance Lease Obligations of $19,098 and $20,115 at September 30, 2021 and December 31, 2020, respectively.