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Transactions with Controlled Companies - Nationwide Loan Company LLC (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Interest Income	$ 184,615	$ 202,447
Interest Receivable	$ 27,486		$ 26,936
Nationwide Loan Company LLC \| Members of Nationwide Management
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest	5.52%
Nationwide Loan Company LLC \| Nationwide Acceptance Holdings LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest	94.48%		94.48%
Reportable Legal Entities \| Subsidiaries \| Nationwide Acceptance Holdings LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Interest Income	$ 1,748	1,175
Interest Income Capitalized as PIK	2,230	785
Interest Receivable	18		$ 501
Other Receivables	2		$ 1
Reportable Legal Entities \| Subsidiaries \| Nationwide Acceptance Holdings LLC \| Prospect Administration
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Managerial Assistance	$ 100	$ 0
Reportable Legal Entities \| Subsidiaries \| Nationwide Acceptance Holdings LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest	100.00%