Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Sales of products	$ 142,544	$ 131,017
Cost of sales and other direct production costs	78,676	74,320
Depreciation, depletion and amortization	28,952	25,875
Total cost of sales	107,628	100,195
Gross profit	34,916	30,822
Other operating expenses:
General and administrative	9,206	10,214
Exploration	4,514	2,950
Pre-development	1,252	404
Research and development	683
Other operating expense	690	640
Lucky Friday suspension-related costs	1,581
Provision for closed operations and environmental matters	1,119	1,041
Total other operating expense	19,045	15,249
Income from operations	15,871	15,573
Other income (expense):
Loss on disposal of investments	(167)
Unrealized income (loss) on investments	327	(711)
Loss on derivative contracts	(7,809)
Net foreign exchange loss	(2,262)	(8,203)
Interest and other income	325	88
Interest expense, net of amounts capitalized	(8,522)	(5,711)
Total other expense	(18,108)	(14,537)
(Loss) income before income taxes	(2,237)	1,036
Income tax benefit (provision)	29,071	(1,654)
Net income (loss)	26,834	(618)
Preferred stock dividends	(138)	(138)
Income (loss) applicable to common stockholders	26,696	(756)
Comprehensive income:
Net income (loss)	26,834	(618)
Reclassification of disposal and impairment of investments included in net income	167	1,000
Unrealized holding (losses) gains on investments	(256)	65
Unrealized gain (loss) and amortization of prior service on pension plans	32
Change in fair value of derivative contracts designated as hedge transactions	3,261
Comprehensive income	$ 30,038	$ 447
Basic income per common share after preferred dividends (in dollars per share)	$ 70
Diluted income per common share after preferred dividends (in dollars per share)	$ 70
Weighted average number of common shares outstanding - basic (in shares)	395,370	379,022
Weighted average number of common shares outstanding - diluted (in shares)	398,149	379,022