Investment Securities: Schedule of Contractual maturities of debt securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Held-to-maturity Securities, Amortized Cost:
Due within one year	$ 3,027
Due after one year to five years	162,601
Due after five years to ten years	38,770
Due after ten years	62,210
Total	266,608	$ 69,102
Held-to-maturity Securities, Estimated Fair Value:
Due within one year	2,983
Due after one year to five years	154,206
Due after five years to ten years	34,197
Due after ten years	58,397
Total	249,783	70,109
Available-for-sale Securities, Amortized Cost:
Due within one year	0
Due after one year to five years	3,169
Due after five years to ten years	9,252
Due after ten years	29,888
Total	42,309	$ 63,080
Available-for-sale Securities, Estimated Fair Value:
Due within one year	0
Due after one year to five years	3,159
Due after five years to ten years	9,152
Due after ten years	29,104
Total	$ 41,415