Debt (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended	6 Months Ended						0 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended
	Feb. 28, 2010 MW	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Minimum	Feb. 28, 2010 Capital Lease	Jun. 30, 2012 Convertible Debt	Jun. 30, 2012 Convertible Debt Maximum	Jun. 30, 2012 Equipment financing credit facility Line of Credit	Jun. 30, 2012 Equipment financing credit facility Line of Credit Caterpillar Financial Services Corporation	Mar. 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	May 31, 2012 4.00% Convertible Debentures Convertible Debt	Jun. 30, 2012 4.00% Convertible Debentures Convertible Debt	Nov. 30, 2007 4.00% Convertible Debentures Convertible Debt	Jun. 30, 2012 5.00% Convertible Debentures Convertible Debt	Jun. 30, 2012 5.00% Convertible Debentures Convertible Debt	May 31, 2012 5.00% Convertible Debentures Convertible Debt
Line of Credit Facility [Line Items]
Credit facility borrowing capacity										$ 31,500,000	$ 40,000,000
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%
Oustanding amount of convertible debenture															50,500,000				77,500,000
Debt instrument aggregate principal amount																125,000,000
Debt amount exchanged with private holders														74,500,000
Number of shares issuable upon conversion (shares)									46.7
Conversion price per share (dollars per share)															$ 5.00		$ 1.65	$ 1.65
Share issue value (percent)								95.00%										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
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		582,000	0	582,000	0									(600,000)
Fair value of outstanding debentures														73,600,000					74,200,000
Debt Issuance Cost																	$ 2,100,000