Quarterly report pursuant to Section 13 or 15(d)

Convertible Preferred Stock and Warrants (Details)

Convertible Preferred Stock and Warrants (Details) $ / shares in Units, $ in Millions			6 Months Ended
	Apr. 09, 2019 USD ($) Agreement $ / shares shares	Apr. 05, 2019 shares	Jun. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 $ / shares
Class Of Stock [Line Items]
Number of underwriting agreements \| Agreement	2
Aggregate gross proceeds from public offerings \| $	$ 70.0
Underwriting discounts and commissions and estimated offering expenses payable \| $	$ 5.0
Preferred stock, par value (in dollars per share) \| $ / shares			$ 0.001	$ 0.001
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Share price (in dollars per share) \| $ / shares			$ 6.57
Minimum ownership percentage to total number stock Issued and outstanding holder is prohibited from conversion	9.99%
Notice period for change in owning percentage	61 days
Convertible preferred stock beneficial conversion feature \| $			$ 0.6
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.001
Class A Warrants
Class Of Stock [Line Items]
Warrants to purchase common stock \| shares			2,118,344
Notice period for change in owning percentage			61 days
Warrant exercise price of common stock per share \| $ / shares			$ 8.625
Warrants exercisable date			Oct. 10, 2022
Maximum ownership percentage to total number stock issued and outstanding holder is prohibited from conversion			4.99%
Change fair value of warrants \| $			$ 9.0
Class A Warrants \| Weighted Average Volatility \| Weighted Average
Class Of Stock [Line Items]
Fair value of weighted average volatility			86.06%
Class A Warrants \| Weighted Average Expected Term \| Weighted Average
Class Of Stock [Line Items]
Fair value of weighted expected term			3 years 6 months
Common Stock \| Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of series A stock into common stock \| shares	1,000	1,000
Minimum ownership percentage to total number stock Issued and outstanding holder is prohibited from conversion		9.99%
Notice period for change in owning percentage		61 days
Public Offering \| Common Stock Agreement \| Class A Warrants
Class Of Stock [Line Items]
Warrants to purchase common stock \| shares	1,951,844
Share price (in dollars per share) \| $ / shares	$ 7.50		$ 7.50
Public Offering \| Common Stock Agreement \| Common Stock
Class Of Stock [Line Items]
Shares issued \| shares	8,667,333
Public Offering \| Preferred Stock Agreement \| Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Shares issued \| shares	666
Public Offering \| Preferred Stock Agreement \| Class A Warrants
Class Of Stock [Line Items]
Warrants to purchase common stock \| shares	166,500
Share price (in dollars per share) \| $ / shares	$ 7,500