Stockholders' Equity and Warrant Liabilities - Additional Information (Details) - USD ($)									2 Months Ended	3 Months Ended				6 Months Ended	9 Months Ended	12 Months Ended
	Aug. 06, 2020	Aug. 01, 2020	Jun. 16, 2020	May 08, 2020	Jan. 09, 2020	Jan. 08, 2020	Oct. 04, 2019	May 03, 2017	Aug. 06, 2020	Sep. 10, 2020	Jul. 31, 2020	Jan. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Aug. 24, 2020	May 11, 2020	Nov. 22, 2019
Stockholders' Equity Note
Common stock, shares authorized											337,500,000			337,500,000	337,500,000	225,000,000		112,500,000
Common stock, par value											$ 0.0001			$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares issued											236,172,797			236,172,797	236,172,797	193,608,684
Expected volatility						103.70%									111.97%	96.00%
Risk-free interest rate						1.81%									0.39%	1.63%
Common stock price per share						$ 2.29					$ 2.23			$ 2.23	$ 2.23	$ 0.24
Expected life (years)																8 years
Class of warrants or rights issued value																$ 3,900,000
Class of warrants or rights charge											$ 1,700,000	$ 23,700,000			$ 15,600,000
Reclassification of estimated fair value of warrant liability to additional paid in capital																$ 26,000,000.0
Warrants outstanding amount											17,200,000			$ 17,200,000	$ 17,200,000
Share based compensation arrangement by share based payment award grant date fair value of awards											$ (434,000)
Series C Warrants [Member]
Stockholders' Equity Note
Class of warrant or right, outstanding											964,114			964,114	964,114	964,114
2018 Omnibus Incentive Plan [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues				4,333,333
Stock or units available for distributions				1,000,000
Excess stock, shares issued				4,000,000
Sale of common stock, net of fees (in shares)				4,333,333
Subsequent Event [Member] | 2018 Omnibus Incentive Plan [Member]
Stockholders' Equity Note
Number of shares reserved for future issuance and sale																	1,503,068
Common Stock [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues											25,144,704	7,938,228	43,997,807
Sale of common stock, net of fees (in shares)											25,144,704	7,938,228	43,997,807
Common Stock [Member] | Series C Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights exercised											0			0	0
Common Stock [Member] | Series D Warrants [Member]
Stockholders' Equity Note
Class of warrants or rights exercised												0
Maximum [Member] | 2018 Omnibus Incentive Plan [Member]
Stockholders' Equity Note
Share based compensation arrangement by share based payment award grant date fair value of awards				$ 250,000,000
Minimum [Member] | 2018 Omnibus Incentive Plan [Member]
Stockholders' Equity Note
Share based compensation arrangement by share based payment award grant date fair value of awards				$ 200,000,000
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	8,000,000	6,000,000
Sale of common stock, net of fees (in shares)					9,396,320
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																$ 0.31
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] | 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 [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] | Exercise Price 0.242 [Member] | Second Funding Warrants [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] | Exercise Price 0.620 [Member] | Second 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																			$ 0.62
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Exercise Price 0.620 [Member] | Second Funding [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
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Exercise Price 0.310 [Member] | Initial Funding Warrants [Member]
Stockholders' Equity Note
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 0.31
Class of warrants or rights exercised					12,000,000
At Market Issuance Sales Agreement [Member] | Common Stock [Member] | Subsequent Event [Member]
Stockholders' Equity Note
Number of shares reserved for future issuance and sale										2,700,000
Stock issued during period, shares, new issues	3,200,000								28,300,000	72,300,000
Average sale price per share	$ 2.51								$ 2.55
Stock issued during period on sales agreement	$ 7,800,000								$ 70,100,000
Sales commissions paid to agent	200,000								2,200,000
Stock issued during period on sales agreement	$ 8,000,000.0								$ 72,300,000
Sale of common stock, net of fees (in shares)	3,200,000								28,300,000	72,300,000
At Market Issuance Sales Agreement [Member] | Maximum [Member] | Common Stock [Member]
Stockholders' Equity Note
Aggregate offering price			$ 75,000,000
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
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
Sale of common stock, net of fees (in shares)											0				7,900,000
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
At Market Issuance Sales Agreement [Member] | Jefferies LLC [Member] | Common Stock [Member]
Stockholders' Equity Note
Aggregate offering price			$ 75,000,000
Percentage of sales commission			3.00%
Stock issued during period, shares, new issues			25,100,000
Average sale price per share														$ 2.56
Stock issued during period on sales agreement														$ 62,300,000
Sales commissions paid to agent														1,900,000
Stock issued during period on sales agreement														$ 64,300,000
Sale of common stock, net of fees (in shares)			25,100,000
At Market Issuance Sales Agreement [Member] | Jefferies LLC [Member] | Common Stock [Member] | Subsequent Event [Member]
Stockholders' Equity Note
Stock issued during period on sales agreement		$ 1,100,000
Underwritten Public Offering [Member]
Stockholders' Equity Note
Stock issued during period, shares, new issues								1,000,000
Sale of common stock, net of fees (in shares)								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