Summary of Significant Accounting Policies and Select Balance Sheet Information - Summary of Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Schedule of Investments [Line Items]
Other assets, net	$ 4,269	$ 2,124
ViaCyte, Inc. [Member]
Schedule of Investments [Line Items]
Other assets, net		479
Operating Lease Right-of-Use Assets [Member]
Schedule of Investments [Line Items]
Other assets, net	2,508
Other Noncurrent Assets [Member]
Schedule of Investments [Line Items]
Other assets, net	$ 1,761	$ 1,645