Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Sales of products	$ 161,532	$ 143,649	$ 448,321	$ 430,617
Cost of sales and other direct production costs	95,878	93,609	311,202	246,918
Depreciation, depletion and amortization	50,774	43,464	139,038	103,335
Total cost of sales	146,652	137,073	450,240	350,253
Gross profit	14,880	6,576	(1,919)	80,364
Other operating expenses:
General and administrative	7,978	10,327	26,855	27,849
Exploration	4,808	12,411	13,556	27,609
Pre-development	881	1,195	2,535	3,615
Research and development	53	1,269	614	5,042
Other operating expense	437	448	1,681	1,767
Loss (gain) on disposition of properties, plants, equipment and mineral interests	24	(3,208)	4,666	(3,374)
Provision for closed operations and reclamation	1,907	1,852	3,529	4,534
Suspension-related costs	3,722	6,519	8,766	18,337
Acquisition costs	183	6,139	593	9,656
Total other operating expense	19,993	36,952	62,795	95,035
Income (loss) from operations	(5,113)	(30,376)	(64,714)	(14,671)
Other income (expense):
(Loss) gain on derivative contracts	(4,718)	19,460	(2,719)	40,271
Gain (loss) on disposition of investments	927	(36)	927	(36)
Unrealized loss on investments	(126)	(2,207)	(1,159)	(2,461)
Foreign exchange gain (loss)	773	(2,212)	(6,741)	2,856
Other expense	(1,096)	(346)	(3,407)	(294)
Interest expense	(11,777)	(10,146)	(33,777)	(30,019)
Total other (expense) income	(16,017)	4,513	(46,876)	10,317
Loss before income taxes	(21,130)	(25,863)	(111,590)	(4,354)
Income tax benefit	1,614	2,679	20,009	1,484
Net loss	(19,516)	(23,184)	(91,581)	(2,870)
Preferred stock dividends	(138)	(138)	(414)	(414)
Loss applicable to common shareholders	(19,654)	(23,322)	(91,995)	(3,284)
Comprehensive loss:
Net loss	(19,516)	(23,184)	(91,581)	(2,870)
Change in fair value of derivative contracts designated as hedge transactions	(3,288)	3,743	4,511	(3,533)
Unrealized holding gains on investments	0	3	0	13
Comprehensive loss	$ (22,804)	$ (19,438)	$ (87,070)	$ (6,390)
Basic loss per common share after preferred dividends (in dollars per share)	$ (0.04)	$ (0.05)	$ (0.19)	$ (0.01)
Diluted loss per common share after preferred dividends (in dollars per share)	$ (0.04)	$ (0.05)	$ (0.19)	$ (0.01)
Weighted average number of common shares outstanding - basic (in shares)	489,971	452,636	486,298	417,532
Weighted average number of common shares outstanding - diluted (in shares)	489,971	452,636	486,298	417,532
Cash dividends declared per common share (in dollars per share)	$ 0.0025	$ 0.0025	$ 0.0075	$ 0.0075