Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue		$ 832,828	$ 785,461	$ 711,502
COSTS AND EXPENSES
Write-downs		0	0	250,814
Amortization		128,315	131,387	178,876
General and administrative		40,399	33,722	34,493
Pre-development, reclamation, and other		48,678	55,654	18,421
Total costs and expenses		780,100	703,741	1,056,312
OTHER INCOME (EXPENSE), NET
Loss on debt extinguishments		(9,173)	0	(1,281)
Fair value adjustments, net, pretax		(543)	7,601	16,030
Interest expense, net of capitalized interest		(16,451)	(20,708)	(24,771)
Other, net		(22,925)	(5,941)	(3,193)
Total other income (expense), net		(49,092)	(19,048)	(13,215)
Income (loss) before income and mining taxes		3,636	62,672	(358,025)
Income and mining tax (expense) benefit		(34,958)	(37,045)	11,129
Income (loss) from continuing operations		(31,322)	25,627	(346,896)
NET INCOME (LOSS)		(31,322)	25,627	(341,203)
OTHER COMPREHENSIVE INCOME (LOSS), Net of Tax:
Unrealized gain (loss) on hedger, net of tax		22,783	(12,434)	(136)
Reclassification adjustments for realized (gain) loss on cash flow hedges		12,859	(1,434)	0
Unrealized gain (loss) on debt and equity securities		0	0	59
Other comprehensive income (loss)		9,924	(11,000)	(77)
COMPREHENSIVE INCOME (LOSS)		$ (21,398)	$ 14,627	$ (341,280)
Income (Loss) from Continuing Operations, Per Basic Share		$ (0.13)	$ 0.11	$ (1.59)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share		0	0	0.03
Basic EPS
Earnings Per Share, Basic		(0.13)	0.11	(1.56)
Income (Loss) from Continuing Operations, Per Diluted Share		(0.13)	0.11	(1.59)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share		0	0	0.03
Diluted EPS
Earnings Per Share, Diluted		$ (0.13)	$ 0.11	$ (1.56)
Income (loss) from discontinued operations		$ 0	$ 0	$ 5,693
Accumulated Deficit [Member]
OTHER INCOME (EXPENSE), NET
NET INCOME (LOSS)		(31,322)	25,627	(341,203)
Product
COSTS AND EXPENSES
Costs applicable to sales	[1]	511,539	440,335	551,181
Mineral, Exploration
COSTS AND EXPENSES
Costs applicable to sales		$ 51,169	$ 42,643	22,527
Write-downs				$ 250,814

[1] Excludes amortization.