Condensed Financial Information - Parent Company Only: Condensed Statements of Operations, Parent Company (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Operating income
Interest on deposits in banks									$ 8,220	$ 7,905	$ 7,143
Interest on investment securities									8,197	9,129	9,384
Income before income taxes and equity in undistributed     income of Bank	$ 10,308	$ 8,890	$ 8,460	$ 8,573	$ 7,927	$ 7,459	$ 7,178	$ 7,842	36,231	30,406	33,994
Benefit for income taxes	1,861	1,790	1,705	1,714	1,572	1,535	1,470	1,546	7,070	6,123	6,876
Net income	$ 8,447	$ 7,100	$ 6,755	$ 6,859	$ 6,355	$ 5,924	$ 5,708	$ 6,296	29,161	24,283	27,118
Parent Company
Operating income
Interest on deposits in banks									0	0	0
Interest on investment securities									29	24	24
Dividends from Bank									12,000	14,000	11,400
Total operating income									12,029	14,024	11,424
Operating expenses									441	328	351
Income before income taxes and equity in undistributed     income of Bank									11,588	13,696	11,073
Benefit for income taxes									(172)	(145)	(148)
Income before undistributed income of Bank									11,760	13,841	11,221
Equity in undistributed income of Bank									17,401	10,442	15,897
Net income									$ 29,161	$ 24,283	$ 27,118