Consolidated Statements of Operations and Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Sales of products	$ 321,143	$ 477,634	$ 418,813
Cost of sales and other direct production costs	134,105	165,573	163,983
Depreciation, depletion and amortization	43,522	47,066	60,011
Total cost of sales	177,627	212,639	223,994
Gross profit	143,516	264,995	194,819
Other operating expenses:
General and administrative	21,253	18,540	18,219
Exploration	31,822	26,959	21,605
Pre-development	17,916	4,446
Other operating expense	4,423	7,658	5,334
Loss on disposition of property, plants, equipment and mineral interests	275		80
Lucky Friday suspension-related costs	25,309
Provision for closed operations and environmental matters	4,652	9,747	201,136
Total other operating expense	105,650	67,350	246,374
Income (loss) from operations	37,866	197,645	(51,555)
Other income (expense):
Gain (loss) on derivative contracts	(10,457)	37,988	(20,758)
Net gain on sale of investments		611	588
Loss on impairment of investments	(1,171)	(140)	(739)
Interest and other income (expense)	22	(87)	126
Interest expense	(2,427)	(2,875)	(2,211)
Total other income (expense):	(14,033)	35,497	(22,994)
Income (loss) before income taxes	23,833	233,142	(74,549)
Income tax benefit (provision)	(8,879)	(81,978)	123,532
Net income	14,954	151,164	48,983
Unrealized gain (loss) and amortization of prior service on pension plans	(1,644)	(7,754)	(1,653)
Unrealized holding gains (losses) on investments	53	(767)	(21)
Reclassification of impairment of investments included in net income	1,171	140	739
Total change in accumulated other comprehensive loss, net	(420)	(8,381)	(935)
Comprehensive income	14,534	142,783	48,048
Basic income per common share after preferred dividends (in Dollars per share)	$ 0.05	$ 0.54	$ 0.14
Diluted income per common share after preferred dividends (in Dollars per share)	$ 0.05	$ 0.51	$ 0.13
Weighted average number of common shares outstanding – basic (in Shares)	285,375	280,956	251,146
Weighted average number of common shares outstanding – diluted (in Shares)	297,566	297,033	269,601
Preferred stock dividends	(552)	(552)	(13,633)
Income applicable to common shareholders	$ 14,402	$ 150,612	$ 35,350