Stockholders' Equity and Warrant Liabilities - Additional Information (Details) - USD ($)					3 Months Ended			6 Months Ended	12 Months Ended
	Jan. 09, 2020	Jan. 08, 2020	Oct. 04, 2019	May 03, 2017	Apr. 30, 2020	Mar. 31, 2020	Jan. 31, 2020	Apr. 30, 2020	Oct. 31, 2019	Nov. 22, 2019
Stockholders' Equity Note
Common stock, par value					$ 0.0001			$ 0.0001	$ 0.0001
Common stock, shares issued					211,052,401			211,052,401	193,608,684
Expected volatility		103.70%					104.90%	107.40%	96.00%
Risk-free interest rate		1.81%					1.45%	0.57%	1.63%
Common stock price per share		$ 2.29			$ 2.02		$ 1.59	$ 2.02	$ 0.24
Expected life (years)									8 years
Class of warrants or rights issued value									$ 3,900,000
Class of warrants or rights charge					$ 3,400,000	$ 23,700,000	$ 10,500,000
Reclassification of estimated fair value of warrant liability to additional paid in capital									$ 26,000,000.0
Warrants outstanding amount					$ 15,500,000			$ 15,500,000
Series C Warrants [Member]
Stockholders' Equity Note
Class of warrant or right, outstanding					964,114			964,114	964,114
Common Stock [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues							7,938,228
Common Stock [Member] | Series C Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights exercised					0			0
Common Stock [Member] | Series D Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights exercised							0
Orion Energy Partners Investment Agent, LLC Credit Facility [Member]
Stockholders' Equity Note
Number of shares reserved for future issuance and sale	2,603,680
Stock issued during period, shares, new issues	9,396,320
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.242
Class of warrant or right, outstanding	8,000,000				8,000,000			8,000,000	6,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Initial Funding Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights issued									6,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights									$ 0.310
Class of warrant or right term								8 years
Class of warrant or right issued to purchase common stock	6,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Initial Funding Warrants [Member] | Exercise Price 0.310 [Member]
Stockholders' Equity Note
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.310
Class of warrants or rights exercised	12,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights issued										14,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding Warrants [Member] | Exercise Price 0.242 [Member]
Stockholders' Equity Note
Class of warrants or rights issued										8,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights										$ 0.242
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding Warrants [Member] | Exercise Price 0.620 [Member]
Stockholders' Equity Note
Class of warrants or rights issued										6,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights										$ 0.620
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member]
Stockholders' Equity Note
Class of warrant or right issued to purchase common stock	6,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | Exercise Price 0.620 [Member]
Stockholders' Equity Note
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.62
Class of warrants or rights exercised	12,000,000
At Market Issuance Sales Agreement [Member] | B. Riley FBR, Inc [Member]
Stockholders' Equity Note
Percentage of sales commission			3.00%
Number of shares reserved for future issuance and sale			27,900,000
Reserve for issuance of common stock upon exercise of warrants shares									20,000,000.0
At Market Issuance Sales Agreement [Member] | B. Riley FBR, Inc [Member] | Common Stock [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues					0			7,900,000
Average sale price per share					$ 0.46			$ 0.46
Stock issued during period on sales agreement								$ 3,600,000
Sales commissions paid to agent								100,000
Net proceeds on sales agreement								$ 3,500,000
Shares available for issuance					1,154			1,154
At Market Issuance Sales Agreement [Member] | B. Riley FBR, Inc [Member] | Maximum [Member]
Stockholders' Equity Note
Aggregate offering price			$ 38,000,000.0
Number of shares reserved for future issuance and sale									7,900,000
Common stock, shares issued									18,000,000.0
Underwritten Public Offering [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues				1,000,000
Underwritten Public Offering [Member] | Series C Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights issued				1,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 19.20
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				1,000,000