Employee Benefits - Additional Information (Detail) - USD ($)	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 1,110,000	$ 1,395,000
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 1,302,000