Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Sales of products	$ 136,925	$ 152,617
Cost of sales and other direct production costs	85,887	110,386
Depreciation, depletion and amortization	39,666	38,787
Total cost of sales	125,553	149,173
Gross profit	11,372	3,444
Other operating expenses:
General and administrative	8,939	9,959
Exploration	2,530	4,402
Pre-development	535	856
Research and development	0	403
Other operating expense	915	587
Gain on disposition of properties, plants, equipment and mineral interests	(104)	0
Ramp-up and suspension costs	12,996	2,778
Acquisition costs	5	13
Provision for closed operations and environmental matters	516	570
Total other operating expense	26,332	19,568
Loss from operations	(14,960)	(16,124)
Other income (expense):
Unrealized (loss) gain on investments	(978)	96
Gain (loss) on derivative contracts	7,893	(1,799)
Net foreign exchange gain (loss)	6,636	(3,133)
Other expense	(527)	(1,124)
Interest expense	(16,311)	(10,665)
Total other expense	(3,287)	(16,625)
Loss before income taxes	(18,247)	(32,749)
Income tax benefit	1,062	7,216
Net loss	(17,185)	(25,533)
Preferred stock dividends	(138)	(138)
Loss applicable to common stockholders	(17,323)	(25,671)
Comprehensive loss:
Net loss	(17,185)	(25,533)
Change in fair value of derivative contracts designated as hedge transactions	(19,335)	4,259
Comprehensive loss	$ (36,520)	$ (21,274)
Basic loss per common share after preferred dividends (in dollars per share)	$ (0.03)	$ (0.05)
Diluted loss per common share after preferred dividends (in dollars per share)	$ (0.03)	$ (0.05)
Weighted average number of common shares outstanding - basic (in shares)	523,215	482,829
Weighted average number of common shares outstanding - diluted (in shares)	523,215	482,829
Cash dividends per common share (in dollars per share)	$ 0.0025	$ 0.0025