Captive Insurance Collateral - Schedule of Maturities of Investments (Detail) - USD ($) $ in Thousands		Sep. 30, 2019	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Due within one year		$ 9,958
Due after one year through five years		35,114
Due after five years through ten years		13,418
Total	[1]	$ 58,490	$ 45,419

[1] See Note 2 – Summary of Significant Accounting Policies - Captive Insurance Collateral.