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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 |  |  |  |  |  |  |  |  |  |  |

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