Fair Value Measurements - Schedule of Carrying Values and Estimated Fair Values of Other Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Carrying Amount
Financial assets
Total financial assets	$ 5,461	$ 9,449
Financial liabilities
Total financial liabilities	1,027,231	1,025,349
Carrying Amount | Senior Notes
Financial liabilities
Total financial liabilities		948,945
Carrying Amount | Junior Subordinated Notes
Financial liabilities
Total financial liabilities		76,404
Fair Value
Financial assets
Total financial assets	5,461	9,584
Financial liabilities
Total financial liabilities	1,015,745	1,052,898
Fair Value | Senior Notes
Financial liabilities
Total financial liabilities	938,308	976,494
Fair Value | Junior Subordinated Notes
Financial liabilities
Total financial liabilities	$ 77,437	$ 76,404