Commitments and contingencies (Details)				3 Months Ended
	Dec. 10, 2015 USD ($) shares	Dec. 20, 2013 $ / shares	Dec. 10, 2013 USD ($) $ / shares	Mar. 31, 2016 USD ($) Lawsuit d shares	Mar. 31, 2015 USD ($)	Feb. 26, 2016 Motion	Jan. 05, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Jun. 02, 2015 shares	Jun. 13, 2014 Lawsuit
Loss Contingencies [Line Items]
Potential future payments				$ 7,500,000
Potential future milestone payments on each additional final marketing approval				$ 1,000,000
Number of purported securities class action lawsuits pending | Lawsuit										3
Number of shareholders lawsuits | Lawsuit				3
Number of day's court afforded the plaintiffs to amend their complaint | d				30
Litigation settlement payment	$ 4,000,000			$ 700,000	$ 0
Litigation settlement due in shares				$ 5,200,000				$ 4,500,000
Common stock issued (in shares) | shares				66,580,065				66,480,065
Options outstanding (in shares) | shares									2,095,000
Exercise price (in dollars per share) | $ / shares		$ 4.66	$ 2.39
Fees and expenses related to settlement			$ 1,100,000
Number of motions filed by the company | Motion						2
Accrued litigation settlement expense				$ 2,000,000
Litigation accounts receivable				900,000
Litigation setttlement				$ 5,200,000
Minimum [Member]
Loss Contingencies [Line Items]
Legal fees to be reimbursed by insurance carrier	$ 3,500,000
Common stock issued (in shares) | shares	1,200,000
Maximum [Member]
Loss Contingencies [Line Items]
Common stock issued (in shares) | shares	1,800,000
Litigation settlement due in shares of common [Member]
Loss Contingencies [Line Items]
Litigation settlement due in shares	$ 4,500,000
Corporation Stockholder Derivative Litigation [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Common stock issued (in shares) | shares							186,666
Corporation Stockholder Derivative Litigation [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Common stock issued (in shares) | shares							280,000
Corporation Stockholder Derivative Litigation [Member] | Litigation settlement due in shares of common [Member]
Loss Contingencies [Line Items]
Litigation settlement due in shares							$ 700,000