Consolidated Statements of Operations and Comprehensive Income (Loss) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements of Operations and Comprehensive Loss [Abstract]
Sales of metal	$ 1,021,200	$ 515,457	$ 300,361
Production costs applicable to sales	(419,956)	(257,636)	(191,311)
Depreciation and depletion	(224,500)	(141,619)	(81,376)
Gross profit	376,744	116,202	27,674
COSTS AND EXPENSES
Administrative and general	31,379	24,176	22,070
Explorations	19,128	14,249	13,056
Pre-development, care, maintenance and other	19,441	2,877	1,468
Total costs and expenses	69,948	41,302	36,594
OPERATING INCOME (LOSS)	306,796	74,900	(8,920)
OTHER INCOME AND EXPENSE
Gain (loss) on debt extinguishments	(5,526)	(20,300)	31,528
Fair value adjustments, net	(52,050)	(117,094)	(82,227)
Interest and other income (expense)	(6,610)	771	1,648
Interest expense, net of capitalized interest	(34,774)	(30,942)	(18,102)
Total other income and expense	98,960	(167,565)	(67,153)
Income (loss) from continuing operations before income taxes	207,836	(92,665)	(76,073)
Income tax benefit (expense)	(114,337)	9,481	33,071
Income (loss) from continuing operations	93,499	(83,184)	(43,002)
Income (loss) from discontinued operations, net of income taxes		(6,029)	(9,601)
Income (loss) on sale of net assets of discontinued operations, net of taxes of $0.0 million for 2011 and $0.0 million for 2010		(2,095)	25,537
NET INCOME (LOSS)	93,499	(91,308)	(27,066)
Other comprehensive loss	(4,975)	(5)
COMPREHENSIVE INCOME (LOSS)	$ 88,524	$ (91,313)	$ (27,066)
Basic income (loss) per share:
Income (loss) from continuing operations	$ 1.05	$ (0.95)	$ (0.60)
Income (loss) from discontinued operations		$ (0.10)	$ 0.22
Net income (loss)	$ 1.05	$ (1.05)	$ (0.38)
Diluted income (loss) per share:
Income (loss) from continuing operations	$ 1.04	$ (0.95)	$ (0.60)
Income (loss) from discontinued operations		$ (0.10)	$ 0.22
Net income (loss)	$ 1.04	$ (1.05)	$ (0.38)
Weighted average number of shares of common stock:
Basic	89,383	87,185	71,565
Diluted	89,725	87,185	71,565