Consolidated Statements of Operations and Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Sales	$ 718,905	$ 807,473	$ 691,873
Cost of sales and other direct production costs	458,811	417,879	382,663
Depreciation, depletion and amortization	143,938	171,793	148,110
Total cost of sales	602,749	589,672	530,773
Gross profit	116,156	217,801	161,100
Other operating expenses:
General and administrative	43,384	34,570	35,561
Exploration and pre-development	46,041	47,901	18,295
Provision for closed operations and environmental matters	8,793	14,571	3,929
Ramp-up and suspension costs	24,114	23,012	24,911
Other operating expense	6,262	14,327	11,426
Total other operating expenses	128,594	134,381	94,122
(Loss) income from operations	12,438	83,420	66,978
Other expense:
Fair value adjustments, net	(4,723)	(35,792)	(11,806)
Foreign exchange gain (loss), net	7,211	417	(4,605)
Other net expense	(7,829)	(574)	(2,256)
Interest expense, net	(42,793)	(41,945)	(49,569)
Total other expense:	(32,476)	(77,894)	(68,236)
(Loss) income before income and mining taxes	(44,914)	5,526	(1,258)
Income and mining tax benefit (provision)	7,566	29,569	(8,199)
Net (loss) income	(37,348)	35,095	(9,457)
Preferred stock dividends	(552)	(552)	(552)
Net (loss) income applicable to common shares	(37,900)	34,543	(10,009)
Comprehensive income (loss):
Net (loss) income	(37,348)	35,095	(9,457)
Unrealized gain (loss) and amortization of prior service on pension plans	(17,067)	16,740	(3,559)
Unrealized gain (loss) on derivative contracts designated as hedge transactions	13,837	(12,307)	7,980
Total change in accumulated other comprehensive income (loss), net	30,904	4,433	4,421
Comprehensive (loss) income	$ (6,444)	$ 39,528	$ (5,036)
Basic (loss) income per common share after preferred dividends	$ 0.07	$ 0.06	$ (0.02)
Diluted (loss) income per common share after preferred dividends	$ 0.07	$ 0.06	$ (0.02)
Weighted average number of common shares outstanding - basic	557,344	536,192	527,329
Weighted average number of common shares outstanding - diluted	557,344	542,176	527,329