Fair Value Measurements - Schedule of Carrying Values and Estimated Fair Values of Other Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Carrying Amount
Financial assets
Total financial assets	$ 9,449	$ 1,951
Financial liabilities
Total financial liabilities	1,025,349	978,028
Carrying Amount | Certificates of Deposit
Financial assets
Certificates of deposit	9,449	1,951
Carrying Amount | Senior Notes
Financial liabilities
Notes	948,945	903,691
Carrying Amount | Junior Subordinated Notes
Financial liabilities
Notes	76,404	74,337
Fair Value
Financial assets
Total financial assets	9,584	1,986
Financial liabilities
Total financial liabilities	1,052,898	932,865
Fair Value | Certificates of Deposit
Financial assets
Certificates of deposit	9,584	1,986
Fair Value | Senior Notes
Financial liabilities
Notes	976,494	858,528
Fair Value | Junior Subordinated Notes
Financial liabilities
Notes	$ 76,404	$ 74,337