Captive Insurance Collateral - Schedule of Maturities of Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Due within one year	$ 14,402
Due after one year through five years	42,552
Due after five years through ten years	8,822
Total	$ 65,776	$ 58,490

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Balance Type:	debit
Period Type:	instant