Stockholders' equity - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended						1 Months Ended					12 Months Ended
	Nov. 09, 2012	May 17, 2012	Dec. 31, 2013	Dec. 31, 2012	Aug. 05, 2009	Nov. 09, 2012 Efftec International Inc	Nov. 09, 2012 Scott Macon Ltd	Jul. 07, 2010 Stock Unit	Mar. 07, 2011 2010 Offering	Mar. 04, 2011 2010 Offering	Jul. 07, 2010 2010 Offering	Aug. 05, 2009 2009 Offering	May 17, 2012 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]	Jul. 07, 2010 Common Stock [Member]
Stockholders Equity [Line Items]
Common stock, issued			25,070,386	24,124,625		133,589	26,716	2,737,500			1,368,750	1,470,000			2,737,500
Common stock, par value			$ 0.01	$ 0.01	$ 1.4375	$ 3.743	$ 3.743				$ 2.00	$ 1.15
Net proceeds from issuance of common stock											$ 4,900,000	$ 1,400,000
Stock issued during period, shares, issued for services												73,500	20,000	20,000
Stock issued during period, value, issued for services		74,000		74,000										0
Class of warrant or right, exercise price of warrants or rights										0.60	2.60
Adjustment of warrants granted for services											1,300,000
Estimated fair value of the warrant												48,000
Class of warrant or right repurchase during period										150,000
Class of warrant or right issued unit during period									1,218,750
Class of warrants expiration date			Jul. 07, 2016
Fair value of shares issued for services	$ 100,000