Condensed Consolidated Statements of Operations (Loss) (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Sales of metal	$ 204,525	$ 254,406	$ 376,322	$ 458,970
Production costs applicable to sales	(142,924)	(131,823)	(231,708)	(224,377)
Depreciation, depletion and amortization	(57,653)	(61,024)	(108,089)	(113,616)
Gross profit	3,948	61,559	36,525	120,977
COSTS AND EXPENSES
Administrative and general	15,026	8,594	25,253	16,190
Exploration	6,774	6,305	13,615	12,872
Litigation settlement	32,046	0	32,046	0
Loss on impairment	86	4,813	205	4,813
Pre-development, care, maintenance and other	973	273	5,458	1,341
Total cost and expenses	54,905	19,985	76,577	35,216
OPERATING INCOME	(50,957)	41,574	(40,052)	85,761
OTHER INCOME AND EXPENSE
Fair value adjustments, net	66,754	16,039	84,550	(7,074)
Other than temporary impairment of marketable securities	(17,192)	0	(17,227)	0
Interest income and other	419	(3,221)	4,275	1,786
Interest expense, net of capitalized interest	(10,930)	(7,557)	(20,662)	(14,227)
Total other income and expense	39,051	5,261	50,936	(19,515)
Income before income taxes	(11,906)	46,835	10,884	66,246
Income tax provision	(23,134)	(23,862)	(33,654)	(39,298)
Net income	$ (35,040)	$ 22,973	$ (22,770)	$ 26,948
Basic income per share:
Net income	$ (0.35)	$ 0.26	$ (0.24)	$ 0.30
Diluted income per share:
Net income	$ (0.35)	$ 0.26	$ (0.24)	$ 0.30
Weighted average number of shares of common stock
Basic	99,833	89,631	94,918	89,611
Diluted	99,833	89,733	94,918	89,777