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Investment Securities - Narrative (Details)	3 Months Ended
	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($) security	Sep. 30, 2025 USD ($) security	Sep. 30, 2023 USD ($)	Jul. 07, 2023 USD ($)
Debt Securities, Available-for-sale [Line Items]
Held-to-maturity, allowance for credit loss		$ 0	$ 0
Number of investment securities in unrealized loss position | security		269	172
Number of investment securities in unrealized loss position longer than 12 months | security			145
Number of investment securities in unrealized loss position less than 12 months | security			27
Debt securities, available-for-sale unrealized loss position, allowance for credit loss		$ 0	$ 0
Interest rate swap | Fair value hedge | Designated as hedging instrument
Debt Securities, Available-for-sale [Line Items]
Derivative, notional amount				$ 101,800,000	$ 101,800,000
Loss on derivative contract termination		$ 0
Debt securities, available-for-sale, sold at par value	$ 69,100,000

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
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-Name Accounting Standards Codification
-Section 45
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