Debt (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended			1 Months Ended				0 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended		9 Months Ended
	Feb. 28, 2010 MW	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Minimum	Feb. 28, 2010 Capital Lease	Sep. 30, 2012 Equipment financing credit facility Line of Credit	Sep. 30, 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	Sep. 30, 2012 4.00% Convertible Debentures Convertible Debt	Nov. 30, 2007 4.00% Convertible Debentures Convertible Debt	Sep. 30, 2012 5.00% Convertible Debentures Convertible Debt	Sep. 30, 2012 5.00% Convertible Debentures Convertible Debt	May 31, 2012 5.00% Convertible Debentures Convertible Debt	Sep. 30, 2012 New Mining Equipment Equipment financing credit facility Line of Credit Caterpillar Financial Services Corporation	Sep. 30, 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	$ 40,000,000
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									19,000,000	22,200,000
Average interest rate on outstanding loans									6.70%	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%	5.00%
Amount of debt redeemed											6,100,000
Discount rate				8.50%
Risk free interest rate				0.63%
Volatility rate				40.00%
Remaining life				4 years 8 months 1 day
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	$ 1.65
Share issue value (percent)																95.00%
Purchase price of convertible debt principal (percentage)						101.00%
Percentage of fair value of consideration paid						10.00%
Convertible debt conversion rate per $1000 principal													200		606.0606
Convertible debt, conversion price above closing stock price (percent)															25.00%	25.00%
Minimum percentage of oustanding debentures required to have accepted mandatory offer to purchase															90.00%	90.00%
Loss on extinguishment of debt		(14,000)	0	568,000	0							(600,000)
Fair value of outstanding debentures												73,600,000	43,800,000		103,900,000	103,900,000	74,200,000
Debt Issuance Cost															$ 2,100,000