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Commitments and Contingencies - Additional Information (Detail) | 1 Months Ended | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jan. 31, 2019 ft² | Mar. 31, 2019 USD ($) ft² | Mar. 31, 2018 USD ($) | Mar. 31, 2019 USD ($) ft² | Mar. 31, 2018 USD ($) | Apr. 30, 2019 ft² | Oct. 31, 2018 USD ($)
Other Commitments [Line Items] |  |  |  |  |  |  |
Facility rent expense |  | $ 436,000 | $ 305,000 | $ 771,000 | $ 630,000 |  |
Provision for recorded liabilities |  | 0 |  | 0 |  |  |
Future commitments |  | 52,100,000 |  | 52,100,000 |  |  |
Commitments expected to be incurred in fiscal 2019 |  | 27,100,000 |  | 27,100,000 |  |  |
Commitments expected to be incurred beyond fiscal 2019 |  | 25,000,000 |  | 25,000,000 |  |  |
Technology License Commitments |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |
Milestone payments |  | $ 0 | $ 0 | $ 0 | $ 0 |  |
Corporate Headquarters In Pasadena | California |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |
Office space leases, in square feet | ft² |  | 8,500 |  | 8,500 |  |  |
Operating lease expiration month and year |  |  |  | 2019-09 |  |  |
Rental expense |  |  |  | $ 31,900 |  |  |
Percentage of increase in annual rental cost |  |  |  | 3.00% |  |  |
Corporate Headquarters In Pasadena | California | Subsequent Event | Colorado Owner, LLC |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |
Office space leases, in square feet | ft² |  |  |  |  |  | 24,000 |
Research Facility in Madison | Wisconsin |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |
Office space leases, in square feet | ft² | 13,000 | 58,000 |  | 58,000 |  |  |
Operating lease expiration month and year | 2029-09 |  |  |  |  |  |
Primary tenant improvement allowance accounted for as deferred rent |  | $ 2,100,000 |  | $ 2,100,000 |  |  |
Promissory note payable |  | $ 2,700,000 |  | 2,700,000 |  |  | $ 2,300,000
Rental expense including payments of principal and interest on the note payable |  |  |  | $ 160,800 |  |  |
Percentage of increase in annual rental cost excluding principal and interest on the note payable |  |  |  | 2.50% |  |  |

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