Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Available-for-sale securities purchased	$ 115,909,000	$ 0
Proceeds from sales of available-for-sale securities	0	4,510,000
Held-to-maturity securities purchased	0	0
Proceeds from sale of held-to-maturity securities	$ 0	$ 0
Term of contractual due dates of substantially all mortgage-backed securities (in years)	10 years
Accrued interest for available-for-sale securities	$ 7,063,000		$ 5,694,000
Accrued interest for held-to-maturity securities	1,084,000		$ 1,108,000
Consumer loans \| Single-family residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Foreclosed residential real estate properties held as REO	93,000
Real estate acquired through foreclosure	$ 2,807,000

Amount, after allowance for credit loss, of accrued interest on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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