Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Debt (Covenant Ratios) (Details) - Maximum	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital											0.0525
Forecast
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital	0.0450	0.0500	0.0450	0.0500	0.0450	0.0500	0.0450	0.0475	0.0525	0.0475