Condensed Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Sales of products	$ 67,019	$ 117,860	$ 158,172	$ 254,224
Cost of sales and other direct production costs	33,172	38,865	66,462	83,394
Depreciation, depletion and amortization	9,879	11,204	19,540	23,466
	43,051	50,069	86,002	106,860
Gross profit	23,968	67,791	72,170	147,364
Other operating expenses:
General and administrative	5,527	4,550	10,028	9,249
Exploration	7,146	5,839	12,757	9,140
Pre-development	3,471		6,837
Other operating expense	1,605	2,270	2,549	4,087
Provision for closed operations and environmental matters	2,235	1,341	4,413	2,362
Lucky Friday suspension-related costs	6,465		12,631
	26,449	14,000	49,215	24,838
Income (loss) from operations	(2,481)	53,791	22,955	122,526
Other income (expense):
Gain on sale of investments				611
Gain (loss) on derivative contracts	6,171	559	940	(1,475)
Interest and other income	32	105	181	123
Interest expense	(505)	(1,496)	(972)	(1,973)
	5,698	(832)	149	(2,714)
Income before income taxes	3,217	52,959	23,104	119,812
Income tax provision	(693)	(19,642)	(8,008)	(43,138)
Net income	2,524	33,317	15,096	76,674
Reclassification of net gain on sale of marketable securities included in net income				(611)
Unrealized holding gains (losses) on investments	(586)	(1,082)	(805)	(115)
Comprehensive income	1,938	32,235	14,291	75,948
Basic income per common share after preferred dividends (in Dollars per share)	$ 0.01	$ 0.12	$ 0.05	$ 0.27
Diluted income per common share after preferred dividends (in Dollars per share)	$ 0.01	$ 0.11	$ 0.05	$ 0.26
Weighted average number of common shares outstanding - basic (in Shares)	285,312	279,347	285,303	278,901
Weighted average number of common shares outstanding - diluted (in Shares)	295,160	295,756	296,100	296,020
Cash dividends declared per common share (in Dollars per share)	$ 0.02		$ 0.04
Preferred stock dividends	(138)	(138)	(276)	(276)
Income applicable to common shareholders	$ 2,386	$ 33,179	$ 14,820	$ 76,398