Debt (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended				0 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended
	Feb. 28, 2010 MW	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 28, 2010 Capital Lease	Dec. 31, 2012 Equipment financing credit facility Line of Credit	Dec. 31, 2012 Equipment financing credit facility Line of Credit Caterpillar Financial Services Corporation	Dec. 31, 2011 Equipment financing credit facility Line of Credit Caterpillar Financial Services Corporation	Sep. 15, 2012 4.00% Convertible Debentures Convertible Debt	May 31, 2012 4.00% Convertible Debentures Convertible Debt	Dec. 31, 2012 4.00% Convertible Debentures Convertible Debt	Nov. 30, 2007 4.00% Convertible Debentures Convertible Debt	Dec. 31, 2012 5.00% Convertible Debentures Convertible Debt	May 31, 2012 5.00% Convertible Debentures Convertible Debt	Dec. 31, 2012 New Mining Equipment Equipment financing credit facility Line of Credit Caterpillar Financial Services Corporation	Dec. 31, 2012 Used Mining Equipment Equipment financing credit facility Line of Credit Caterpillar Financial Services Corporation
Line of Credit Facility [Line Items]
Credit facility borrowing capacity						$ 31,500,000	$ 35,000,000
Repayment period for amounts drawn under credit facility															5 years	2 years
Debt instrument basis spread on variable rate							2.38%
Credit available to draw down							16,800,000	22,200,000
Average interest rate on outstanding loans							6.60%	6.80%
Power plant notional capacity	20
Capital lease obligation					4,900,000
Capital lease monthly payment					300,000
Capital lease monthly payment allocated to principal and interest					230,000
Debt instrument interest rate											4.00%		5.00%
Amount of debt redeemed									6,100,000
Discount rate		8.60%
Risk free interest rate		0.73%
Volatility rate		40.00%
Remaining life		4 years 5 months 0 days
Oustanding amount of convertible debenture											44,400,000			77,500,000
Debt instrument aggregate principal amount												125,000,000
Debt amount exchanged with private holders										74,500,000
Conversion price per share (dollars per share)											$ 5.00		$ 1.65
Share issue value (percent)													95.00%
Convertible debt conversion rate per $1000 principal											200		606.0606
Convertible debt, conversion price above closing stock price (percent)													25.00%
Minimum percentage of oustanding debentures required to have accepted mandatory offer to purchase													90.00%
Loss on extinguishment of debt		568,000	0	0						(600,000)
Fair value of outstanding debentures										73,600,000	0			74,200,000
Debt Issuance Cost													$ 2,100,000