Other Assets - Summary of Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Schedule of Investments [Line Items]
Other assets, net	$ 1,039	$ 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	$ 560	$ 418