Supporting Financial Information - Debt Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Long-term debt	$ 53,800
Less: current portion of bank debt obligations, net of deferred financing costs	0	$ (6,727)
Long-term portion of bank debt obligations, net of deferred financing costs	51,537	60,544
Secured Debt
Debt Instrument [Line Items]
Less: unamortized deferred financing costs	(2,263)	(2,729)
Net bank debt obligations	51,537	67,271
Less: current portion of bank debt obligations, net of deferred financing costs	0	(6,727)
Long-term portion of bank debt obligations, net of deferred financing costs	51,537	60,544
Secured Debt \| Term Loans
Debt Instrument [Line Items]
Long-term debt	$ 53,800	$ 70,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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