Summary of Significant Accounting Policies and Select Balance Sheet Information - Summary of Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Schedule of Investments [Line Items]
Other assets, net	$ 1,446	$ 897
ViaCyte, Inc. [Member]
Schedule of Investments [Line Items]
Other assets, net	479	479
Other Noncurrent Assets [Member]
Schedule of Investments [Line Items]
Other assets, net	$ 967	$ 418