Debt - Additional Information (Detail) (USD $)	12 Months Ended				1 Months Ended		1 Months Ended			1 Months Ended			1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	May 11, 2011	May 31, 2011 Manufacturing Facility Mg l	May 31, 2011 Promissory note Manufacturing Facility	Jun. 30, 2010 Promissory note Purchased equipment	Dec. 31, 2012 Promissory note Purchased equipment	Dec. 31, 2011 Promissory note Purchased equipment	May 11, 2011 Term loan	Dec. 31, 2012 Term loan	Dec. 31, 2011 Term loan	May 11, 2011 Revolving Facility	Dec. 31, 2012 Silicon Valley Bank and Affiliates
Debt Instrument [Line Items]
Amount borrowed						$ 5,500,000	$ 265,000			$ 15,000,000
Final payment due							Jan. 01, 2015
Interest rate							9.00%			5.00%
Outstanding principal amount	14,987,000							129,000	179,000
Credit facility maximum borrowing				20,000,000						15,000,000			5,000,000
Minimum unrestricted cash and investment	30,000,000													25,000,000
Upon financial covenant default, increase in interest rate spread											3.00%
Term of monthly payments										48 months
Maturity date										Nov. 01, 2015			May 10, 2013
Outstanding balance under the credit facility											11,200,000	14,700,000
Fermenters production facility					128,000
Annual oil production capacity					1,820
Annual oil production capacity, in units					2,000,000
Purchase price of production facility					11,500,000
First payment due date of principal						2012-03
Second payment due date of principal						2013-02
Imputed interest rate						3.25%
Amount of discount	19,000					300,000
Weighted average interest rate on outstanding debt	4.60%	4.60%
Interest cost on debt	$ 800,000	$ 600,000	$ 100,000