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Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) |  |  |  |  |  |  | 2 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |
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Aug. 06, 2020 | Jun. 16, 2020 | Apr. 24, 2020 | Apr. 20, 2020 | Nov. 22, 2019 | Nov. 05, 2019 | Aug. 06, 2020 | Sep. 10, 2020 | Jul. 31, 2020 | Jan. 31, 2020 | Jul. 31, 2019 | Jul. 31, 2020 | Jul. 31, 2019 | Oct. 31, 2020 | Oct. 31, 2019 | Jun. 08, 2020
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expenses |  |  |  |  |  |  |  |  | $ 1,027,000 |  | $ 1,977,000 | $ 3,323,000 | $ 12,435,000 |  |  |
Unrestricted cash and cash equivalents |  |  |  |  |  |  |  |  | 66,300,000 |  |  | 66,300,000 |  |  | $ 9,400,000 |
Unrestricted cash and cash equivalents balance excluding amounts funded |  |  |  |  |  |  |  |  | $ 50,100,000 |  |  | 50,100,000 |  |  | 9,400,000 |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of common stock, net of fees (in shares) |  |  |  |  |  |  |  |  | 25,144,704 | 7,938,228 | 43,997,807 |  |  |  |  |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from long-term lines of credit |  |  |  |  |  |  |  |  |  |  |  | 16,200,000 |  |  | 0 |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Senior Secured Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term line of credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 200,000,000.0 |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Initial Funding [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Drew down to fully repay debt outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 14,500,000 |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Drew down to fully repay debt outstanding |  |  |  |  | $ 65,500,000 |  |  |  |  |  |  |  |  |  |  |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Remainder of Funding [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit receivable amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 120,000,000.0 |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Remainder of Funding [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit receivable amount |  |  |  |  |  |  |  |  | $ 120,000,000.0 |  |  | $ 120,000,000.0 |  |  |  |
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Fifth Orion Amendment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 35,000,000
PPP Note [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from promissory note |  |  | $ 6,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Period of utilization of amount from promissory notes |  |  |  | 168 days |  |  |  |  |  |  |  |  |  |  |  |
PPP Note [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of payroll to be utilized from proceeds |  |  |  | 60.00% |  |  |  |  |  |  |  |  |  |  |  |
Joint Development Agreement [Member] | Exxon Mobile Research And Engineering Company [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment for exclusivity and technology access fee |  |  |  |  |  | $ 5,000,000.0 |  |  |  |  |  |  |  |  |  |
Joint Development Agreement [Member] | Maximum [Member] | Exxon Mobile Research And Engineering Company [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expenses |  |  |  |  |  | 45,000,000.0 |  |  |  |  |  |  |  |  |  |
Milestone-based payments |  |  |  |  |  | $ 10,000,000.0 |  |  |  |  |  |  |  |  |  |
Joint Development Agreement [Member] | Scenario Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Milestone payments eligible for achievement |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,000,000 |  |
At Market Issuance Sales Agreement [Member] | Common Stock [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of common stock, net of fees (in shares) | 3,200,000 |  |  |  |  |  | 28,300,000 | 72,300,000 |  |  |  |  |  |  |  |
Average Sale of Stock Price Per Share | $ 2.51 |  |  |  |  |  | $ 2.55 |  |  |  |  |  |  |  |  |
Gross Proceeds From Issuance Of Common Stock | $ 8,000,000.0 |  |  |  |  |  | $ 72,300,000 |  |  |  |  |  |  |  |  |
Payments of Stock Issuance Costs | 200,000 |  |  |  |  |  | 2,200,000 |  |  |  |  |  |  |  |  |
Proceeds from Issuance of Common Stock | $ 7,800,000 |  |  |  |  |  | $ 70,100,000 |  |  |  |  |  |  |  |  |
Common Stock, Reserved for Future Issuance |  |  |  |  |  |  |  | 2,700,000 |  |  |  |  |  |  |  |
At Market Issuance Sales Agreement [Member] | Maximum [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nature Of Business And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate Offering Price |  | $ 75,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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