Stockholders' Equity - Common Stock and Warrants (Details) $ / shares in Units, $ in Thousands						1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 29, 2019 USD ($)	Oct. 15, 2019 shares	Apr. 12, 2017 USD ($) $ / shares shares	Apr. 03, 2017 USD ($) $ / shares	Dec. 22, 2016 $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) item $ / shares shares	Sep. 30, 2018 USD ($) shares	Dec. 31, 2017 shares	Dec. 31, 2018 $ / shares shares	Jul. 20, 2017 $ / shares
Stockholders' equity
Preferred stock, Shares authorized | shares							5,000,000		5,000,000
Preferred stock, par value | $ / shares							$ 0.01		$ 0.01
Common Stock Shares, Outstanding | shares							238,723,533		238,723,533			219,157,998
Common stock, par value (in dollars per share) | $ / shares							$ 0.01		$ 0.01			$ 0.01
Number of votes per share | item									1
Common stock shares issued | shares						10,000,000
Par value, common stock | $ / shares							$ 0.01		$ 0.01			$ 0.01
Share price (in dollars per share) | $ / shares						$ 2.35
Proceeds from public offerings, net of transaction costs | $						$ 23,500			$ 38,098	$ 4,912
Exercise price of warrants (in dollars per share) | $ / shares													$ 2.1231
Number of warrants exercised (in shares) | shares		5,250,750
Value of shares issued | $							$ 9,835	$ 4,902	$ 38,098	$ 4,912
Series A Junior Participating Cumulative Preferred Stock
Stockholders' equity
Preferred stock, par value | $ / shares							$ 0.01		$ 0.01
At Market Issuance Sales Agreement
Stockholders' equity
Common stock, par value (in dollars per share) | $ / shares				$ 0.01
Common stock shares issued | shares									6,300,000
Par value, common stock | $ / shares				$ 0.01
Proceeds from public offerings, net of transaction costs | $									$ 14,800
Authorized amount | $				$ 75,000
Value of shares issued | $	$ 46,800
Gross proceeds from sales of fixed combination of the shares and the warrants | $									$ 15,300
Warrants issued in December 2016
Stockholders' equity
Class of Warrant or Right Issued | shares					10,501,500
Exercise price of warrants (in dollars per share) | $ / shares					$ 1.50
Number of warrants exercised (in shares) | shares			10,501,500
Proceeds from exercise of warrants, net of transaction costs | $			$ 15,100
Shares of common stock that can be purchased from warrants issued | shares			5,250,750
Per share price of shares of common stock | $ / shares			$ 2.69
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Number of warrants exercised (in shares) | shares									26,188,434	18,913,869
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017 | Maximum
Stockholders' equity
Class of Warrant or Right Issued | shares											110,573,392