Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Statement of Income and Comprehensive Income [Abstract]
Sales of metal	$ 204,564	$ 199,624
Production costs applicable to sales	(92,554)	(92,474)
Depreciation, depletion and amortization	(52,592)	(50,041)
Gross profit	59,418	57,109
COSTS AND EXPENSES
Administrative and general	7,596	12,231
Exploration	6,567	2,762
Pre-development, care, maintenance and other	1,068	3,574
Total cost and expenses	15,231	18,567
OPERATING INCOME	44,187	38,542
OTHER INCOME AND EXPENSE
Loss on debt extinguishments	0	(467)
Fair value adjustments, net	(23,113)	(5,302)
Interest income and other	5,007	1,934
Interest expense, net of capitalized interest	(6,670)	(9,304)
Total other income and expense	(24,776)	(13,139)
Income before income taxes	19,411	25,403
Income tax provision	(15,436)	(12,939)
NET INCOME (LOSS)	$ 3,975	$ 12,464
Basic income (loss) per share:
Net income	$ 0.04	$ 0.14
Diluted income (loss) per share:
Net income	$ 0.04	$ 0.14
Weighted average number of shares of common stock
Basic	89,591	89,288
Diluted	89,821	89,653