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%