Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		12 Months Ended
	May 03, 2017	Oct. 31, 2017	Jul. 31, 2017	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2015	Apr. 28, 2017	Jul. 30, 2014
Stockholders' Equity Note
Common stock, shares authorized		125,000,000		125,000,000	75,000,000
Common stock price per share							$ 1.15
NRG Energy, Inc. [Member]
Stockholders' Equity Note
Class of Warrant or Right, Exercise Price of Warrants or Rights								$ 40.20
Class of Warrant or Right, Number of Securities Called by Warrants or Rights								200,000
Warrants expiration date				Jul. 30, 2017
Common Stock [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues				7,245,430	6,023,372	1,845,166
Stock issued during period on open market, net of fees				$ 12.6	$ 36.1
Selling commissions				$ 0.1	$ 0.1
Series C Warrants [Member]
Stockholders' Equity Note
Class of Warrant or Right, Outstanding		11,580,900		11,580,900
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		11,580,900		11,580,900
Series C Warrants [Member] | Common Stock [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues		419,100
Net proceeds from common stock and warrants		$ 0.7
Series D Warrants [Member]
Stockholders' Equity Note
Class of Warrant or Right, Outstanding		2,584,174		2,584,174
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		2,584,174		2,584,174
Series D Warrants [Member] | Common Stock [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues		9,415,826	9,415,826
Net proceeds from common stock and warrants		$ 12.1	$ 12.1
Series A Warrants [Member]
Stockholders' Equity Note
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 5.83		$ 5.83
Class of Warrant or Right, Outstanding		7,680,000		7,680,000
Series B Warrants [Member]
Stockholders' Equity Note
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 0.0001		$ 0.0001
Class of Warrant or Right, Outstanding		4,926,000		4,926,000	3,826,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights					3,826,000
Underwritten Public Offering [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues	12,000,000
Gross proceeds from common stock and warrants	$ 15.4
Common stock price per share	$ 1.28
Net proceeds from common stock and warrants	$ 13.9
Underwritten Public Offering [Member] | Series C Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights issued	12,000,000
Warrants issued, price per share	$ 1.28
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 1.60
Class of warrant or right term	5 years
Underwritten Public Offering [Member] | Series D Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights issued	12,000,000
Warrants issued, price per share	$ 1.28
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 1.28
Class of warrant or right term	1 year