Organization and nature of operations (Details 2)				1 Months Ended
	Jul. 28, 2015 USD ($) $ / shares shares	Jul. 10, 2015	Jun. 30, 2015 USD ($) $ / shares shares	Jul. 27, 2015 USD ($) $ / shares shares	Jul. 27, 2015 USD ($) $ / shares shares
Series C preferred stock | Series C Warrants Issued with Series C Redeemable Preferred Stock Financing
Organization and nature of operations
Number of shares issued upon exercise of warrants			150,000	1,000,000
Exercise price of warrants (in dollars per share) | $ / shares			$ 5.00	$ 5.00	$ 5.00
Proceeds from exercise of warrants (in dollars) | $			$ 750,000	$ 5,000,000
Common Stock | Series C Warrants Issued with Series C Redeemable Preferred Stock Financing | Cashless exercise of redeemable convertible preferred stock warrant into common stock
Organization and nature of operations
Shares issued on conversion	78,926
Common Stock | All series of redeemable convertible preferred stock | Conversion of redeemable convertible preferred stock into common stock
Organization and nature of operations
Shares issued on conversion	9,217,983
IPO | Common Stock
Organization and nature of operations
Shares sold	5,520,000
Public offering price (in dollars per share) | $ / shares	$ 15.00
Net proceeds from issuance of stock | $	$ 75,000,000
Over-allotment option | Common Stock
Organization and nature of operations
Shares sold	720,000
Subsequent event | Series C preferred stock | Series C Warrants Issued with Series C Redeemable Preferred Stock Financing
Organization and nature of operations
Number of shares issued upon exercise of warrants					850,000
Exercise price of warrants (in dollars per share) | $ / shares				$ 5.00	$ 5.00
Proceeds from exercise of warrants (in dollars) | $					$ 4,250,000
Subsequent event | Common Stock
Organization and nature of operations
Reverse stock split ratio		0.4167