Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Sales of metal	$ 230,593	$ 343,575	$ 689,563	$ 774,289
Production costs applicable to sales	(124,967)	(141,253)	(349,344)	(310,829)
Depreciation, depletion and amortization	(52,844)	(58,652)	(166,460)	(166,334)
Gross profit	52,782	143,670	173,759	297,126
COSTS AND EXPENSES
Administrative and general	10,266	8,236	26,456	22,294
Exploration	6,957	4,772	19,829	11,611
Loss on impairment	1,293	0	6,106	0
Pre-development, care, maintenance and other	277	3,271	1,618	17,949
Total cost and expenses	18,793	16,279	54,009	51,854
OPERATING INCOME	33,989	127,391	119,750	245,272
OTHER INCOME AND EXPENSE
Loss on debt extinguishments	0	(784)	0	(1,640)
Fair value adjustments, net	(37,648)	(53,351)	(44,722)	(71,051)
Interest income and other	12,664	(6,610)	14,450	(1,946)
Interest expense, net of capitalized interest	(7,351)	(7,980)	(21,578)	(26,553)
Total other income and expense	(32,335)	(68,725)	(51,850)	(101,190)
Income before income taxes	1,654	58,666	67,900	144,082
Income tax provision	(17,475)	(27,606)	(56,773)	(61,947)
NET INCOME	$ (15,821)	$ 31,060	$ 11,127	$ 82,135
Basic income per share:
Net income	$ (0.18)	$ 0.35	$ 0.12	$ 0.92
Diluted income per share:
Net income	$ (0.18)	$ 0.35	$ 0.12	$ 0.92
Weighted average number of shares of common stock
Basic	89,429	89,449	89,550	89,350
Diluted	89,429	89,739	89,690	89,702