Liquidity and management's plans (Details Textual) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2012 Series A Non-Voting Convertible Preferred Stock [Member]
Liquidity and management's plan (Textual) [Abstract]
Preferred Stock, par value	$ 0.001		$ 0.001		$ 0.001
Liquidity and management's plan (Additional Textual) [Abstract]
Upfront and milestone payments from Endo license agreement			$ 45,000,000
Net proceeds from registered direct offering of Common Stock and newly designated Series			38,400,000
Exercise of Common Stock options			2,100,000
Exercise of Common Stock warrants			900,000
Cash and cash equivalents	49,666,908	32,114,967	63,189,307	10,750,205
Cash from operations	(13,522,399)	22,500,359
Stockholders' equity	$ 39,710,875		$ 49,777,213