Consolidated Statements of Operations and Comprehensive Income (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Sales of products	$ 477,634,000	$ 418,813,000	$ 312,548,000
Cost of sales and other direct production costs	165,573,000	163,983,000	148,642,000
Depreciation, depletion and amortization	47,066,000	60,011,000	62,837,000
Total cost of sales	212,639,000	223,994,000	211,479,000
Gross profit	264,995,000	194,819,000	101,069,000
Other operating expenses:
General and administrative	18,540,000	18,219,000	18,624,000
Exploration	26,959,000	21,605,000	9,247,000
Pre-development	4,446,000
Other operating expense	7,658,000	5,334,000	5,389,000
Loss (gain) on disposition of property, plants, equipment and mineral interests		80,000	(6,234,000)
Termination of employee benefit plan			(8,950,000)
Provision for closed operations and environmental matters	9,747,000	201,136,000	7,721,000
Total other operating expense	67,350,000	246,374,000	25,797,000
Income (loss) from operations	197,645,000	(51,555,000)	75,272,000
Other income (expense):
Gain (loss) on derivative contracts	37,988,000	(20,758,000)
Net gain on sale of investments	611,000	588,000	4,070,000
Loss on impairment of investments	(140,000)	(739,000)	(3,018,000)
Interest and other income (expense)	(87,000)	126,000	1,121,000
Debt-related fees			(5,973,000)
Interest expense	(2,875,000)	(2,211,000)	(11,326,000)
Total other income (expense):	35,497,000	(22,994,000)	(15,126,000)
Income (loss) before income taxes	233,142,000	(74,549,000)	60,146,000
Income tax benefit (provision)	(81,978,000)	123,532,000	7,680,000
Net income	151,164,000	48,983,000	67,826,000
Unrealized gain (loss) and amortization of prior service on pension plans	(7,754,000)	(1,653,000)	6,006,000
Change in fair value of derivative contracts			1,967,000
Unrealized holding gains (losses) on investments	(767,000)	(21,000)	3,498,000
Reclassification of net gain on sale or impairment of investments included in net income	140,000	739,000	(632,000)
Comprehensive income	142,783,000	48,048,000	78,665,000
Basic income per common share after preferred dividends (in Dollars per share)	$ 0.54	$ 0.14	$ 0.24
Diluted income per common share after preferred dividends (in Dollars per share)	$ 0.51	$ 0.13	$ 0.23
Weighted average number of common shares outstanding – basic (in Shares)	280,956	251,146	224,933
Weighted average number of common shares outstanding – diluted (in Shares)	297,033	269,601	233,618
Preferred stock dividends	(552,000)	(13,633,000)	(13,633,000)
Income applicable to common shareholders	$ 150,612,000	$ 35,350,000	$ 54,193,000