Fair Value Measurements - Fair Value Measured on Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	$ 5,805	$ 38,207	$ 5,805	$ 38,207
Loans receivable/Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	4,345	34,535	4,345	34,535
Real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	1,460	3,672	1,460	3,672
Changes measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses)	(2,714)	(10,651)	(4,914)	(16,871)
Changes measurement | Loans receivable/Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses)	(2,679)	(10,530)	(3,004)	(16,773)
Changes measurement | Real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses)	(35)	(121)	(1,910)	(98)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	0	0	0	0
Level 1 | Loans receivable/Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	0	0	0	0
Level 1 | Real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	0	0	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	0	0	0	0
Level 2 | Loans receivable/Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	0	0	0	0
Level 2 | Real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	0	0	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	5,805	38,207	5,805	38,207
Level 3 | Loans receivable/Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	4,345	34,535	4,345	34,535
Level 3 | Real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure	$ 1,460	$ 3,672	$ 1,460	$ 3,672