Condensed Consolidated Statements of Operations and Comprehensive (Loss) Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Sales of products	$ 131,017	$ 119,092
Cost of sales and other direct production costs	74,320	73,965
Depreciation, depletion and amortization	25,875	25,254
	100,195	99,219
Gross profit	30,822	19,873
Other operating expenses:
General and administrative	10,214	8,720
Exploration	2,950	4,615
Pre-development	404	521
Other operating expense	640	628
Provision for closed operations and environmental matters	1,041	467
	15,249	14,951
Income from operations	15,573	4,922
Other income (expense):
Unrealized loss on investments	$ (711)	(2,843)
Gain on derivative contracts		5,792
Net foreign exchange (loss) gain	$ (8,203)	12,274
Interest and other income	88	38
Interest expense, net of amounts capitalized	(5,711)	(6,192)
	(14,537)	9,069
Income before income taxes	1,036	13,991
Income tax provision	(1,654)	(1,439)
Net (loss) income	(618)	12,552
Preferred stock dividends	(138)	(138)
(Loss) income applicable to common stockholders	(756)	12,414
Comprehensive income:
Net (loss) income	(618)	12,552
Reclassification of impairment of investments included in net income	1,000	2,827
Unrealized holding gains (losses) on investments	65	(891)
Comprehensive income	$ 447	$ 14,488
Basic (loss) income per common share after preferred dividends (in dollars per share)		$ 0.03
Diluted (loss) income per common share after preferred dividends (in dollars per share)		$ 0.03
Weighted average number of common shares outstanding - basic (in shares)	379,022	368,789
Weighted average number of common shares outstanding - diluted (in shares)	379,022	369,691