Note 17 - Segment Information - Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
(Loss) Earnings Before Income Tax	$ (4,721)	$ (28,746)	$ 26,868	$ (24,363)
Interest Expense, net	16,187	14,722	31,448	30,393
Gain on Debt Extinguishment	(106)	0	(789)	(16,833)
Interest Income	(811)	(122)	(1,669)	(366)
Depreciation, Depletion and Amortization	52,199	46,155	112,096	101,098
Unrealized Loss on Commodity Derivative Instruments	20,437	0	20,437	0
Pension Settlement	22	0	22	0
Stock/Unit-Based Compensation	1,210	2,236	2,719	7,250
Adjusted EBITDA	$ 84,417	$ 34,245	$ 191,132	$ 97,179