Significant Agreements - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended				3 Months Ended			12 Months Ended		3 Months Ended					3 Months Ended
	Sep. 30, 2012 gal	Sep. 30, 2011 gal	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Ethanol Marketing Agreement with Subsidiary of Mansfield Oil Company	Mar. 31, 2013 Cargill License Agreement Installment	Mar. 31, 2010 Cargill License Agreement	Dec. 31, 2009 Cargill License Agreement	Dec. 31, 2012 Cargill License Agreement	Mar. 31, 2013 Defense Logistics Agency	Mar. 31, 2012 Defense Logistics Agency	Mar. 31, 2013 Coca Cola	Mar. 31, 2012 Coca Cola	Mar. 31, 2013 Toray Industries	Mar. 31, 2013 Development and Commercialization Agreements with ICM Inc
Parties To Contract [Line Items]
Terms of agreement					The ethanol purchase and marketing agreement with C&N was entered into on April 1, 2009 and automatically renews for subsequent one-year terms unless either party terminates the agreement 60 days before the end of a term.	The Company may terminate the license agreement at any time upon 90 days' prior written notice. Unless terminated earlier, the license agreement remains in effect until the later of December 31, 2025 and the date that no licensed patent rights remain.									In December 2011, the development agreement was amended to extend the term indefinitely. The development agreement, as amended, may be cancelled by either party with 30 days' prior written notice.
Production, barrels of oil Equivalents	45,000	11,000
Revenue from contract										$ 0.4	$ 0.2
Revenue recognized under agreement												0.3	0.3
Milestone payment						5
Royalty expense						4.3	2.0	0.9
Present value of license fee							1.6
Royalty Fee Payable						1.0
Royalty Fee Payable, due date						2015-12
License Fees						0.5
License Fees, accrued									0.5
Common Stock Issued			43,966,309	39,606,668		250,000
Amount received for Pilot Plant														1.0
Amount refund from Pilot Plant														1.0
Refund Amount as Component of Other Long Term Liabilities			$ 1.0