Summary of Significant Accounting Policies and Select Balance Sheet Information - Summary of Other Assets (Detail) - USD ($) $ in Thousands |
Sep. 30, 2017 |
Sep. 30, 2016 |
|---|---|---|
| Schedule of Investments [Line Items] | ||
| Other assets, net | $ 897 | $ 628 |
| 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 | $ 418 | $ 149 |