Stockholders' equity (Details 7) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Options or Warrants Outstanding	5,447,992	5,544,671
Exercise Price Range One [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, minimum	$ 1.95	$ 1.95
Exercise Price Range, maximum	$ 6.15	$ 6.15
Number of Options or Warrants Outstanding	998,334	1,003,334
Exercise Price Range Two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, minimum	$ 6.16	$ 6.16
Exercise Price Range, maximum	$ 6.30	$ 6.30
Number of Options or Warrants Outstanding	230,000	230,000
Exercise Price Range Three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, minimum	$ 6.31	$ 6.31
Exercise Price Range, maximum	$ 6.45	$ 6.45
Number of Options or Warrants Outstanding	1,440,000	1,440,000
Exercise Price Range Four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, minimum	$ 6.46	$ 6.46
Exercise Price Range, maximum	$ 7.05	$ 7.05
Number of Options or Warrants Outstanding	1,253,333	1,267,604
Exercise Price Range Five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, minimum	$ 7.20	$ 7.20
Exercise Price Range, maximum	$ 15.00	$ 15.00
Number of Options or Warrants Outstanding	1,526,325	1,603,733