Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Employee Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Employee Benefits (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Contribution Plan Disclosure [Line Items]
Contributions and expenses	$ 2,603	$ 2,466	$ 2,213
Tranche 1
Defined Contribution Plan Disclosure [Line Items]
Employer percent match	100.00%
Percentage of employees' gross pay	3.00%
Tranche 2
Defined Contribution Plan Disclosure [Line Items]
Employer percent match	50.00%
Percentage of employees' gross pay	2.00%