Investment Securities: Other than Temporary Impairment, Credit Losses Recognized in Earnings (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 803	$ 816	$ 836
Net realized losses previously recorded as credit losses	(4)	(2)	(11)
Recovery of prior credit loss	(11)	(11)	(9)
Ending balance	$ 788	$ 803	$ 816