Fair Value Measurements - Schedule of Carrying Values and Estimated Fair Values of Other Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Carrying Amount
Financial assets
Total financial assets	$ 9,362	$ 1,951
Financial liabilities
Total financial liabilities	1,024,408	978,028
Carrying Amount | Senior Notes
Financial liabilities
Total financial liabilities	948,521	903,691
Carrying Amount | Junior Subordinated Notes
Financial liabilities
Total financial liabilities	75,887	74,337
Fair Value
Financial assets
Total financial assets	9,582	1,986
Financial liabilities
Total financial liabilities	1,033,794	932,865
Fair Value | Senior Notes
Financial liabilities
Total financial liabilities	957,907	858,528
Fair Value | Junior Subordinated Notes
Financial liabilities
Total financial liabilities	$ 75,887	$ 74,337