Stockholders' equity - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended			12 Months Ended			0 Months Ended
	May 17, 2012	Dec. 31, 2012	Dec. 31, 2011	Jul. 07, 2010 Warrants	Dec. 31, 2012 Common Stock	Jul. 07, 2010 Common Stock	Jul. 07, 2010 Stock Unit	Aug. 05, 2009 2009 Offering	Mar. 07, 2011 2010 Offering	Mar. 04, 2011 2010 Offering	Jul. 07, 2010 2010 Offering	Aug. 05, 2009 Roth Capital Partners	Jul. 31, 2009 Roth Capital Partners	Aug. 03, 2012 Keltic Financial Partners Lp	May 17, 2012 Keltic Financial Partners Lp	Nov. 09, 2012 Efftec International Inc	Nov. 09, 2012 Scott Macon Ltd
Stockholders Equity [Line Items]
Common stock, issued		24,124,625	23,783,106	1,368,750		2,737,500	2,737,500	1,470,000					3,870,000			133,589	26,716
Common stock, par value		$ 0.01	$ 0.01				$ 2.00	$ 1.15				$ 1.4375	$ 1.15			$ 3.743	$ 3.743
Net proceeds from issuance of common stock								$ 1,400,000			$ 4,900,000
Fees and commissions								101,000
Stock issued during period, shares, issued for services	20,000				20,000							73,500
Stock issued during period, value, issued for services	74,000	74,000			0
Reimbursement revenue												56,000
Class of warrant or right, exercise price of warrants or rights										0.60	2.60				1.88
Adjustment of warrants granted for services											1,300,000
Estimated fair value of the warrant								$ 48,000
Class of warrant or right repurchase during the period										150,000
Class of warrant or right issued unit during the period									1,218,750
Class of warrants expiration date									Jul. 07, 2016
Class of warrant or right, number of securities called by warrants or rights															100,000
Common stock issued upon cashless exercise of warrants														53,140
Fair market value of warrant on exercise date														$ 4.012