Investment Securities: Schedule of Contractual maturities of debt securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Held-to-maturity Securities, Amortized Cost:
Due within one year	$ 0
Due after one year to five years	144
Due after five years to ten years	6,708
Due after ten years	23,808
Total	30,660	$ 31,102	[1]
Held-to-maturity Securities, Estimated Fair Value:
Due within one year	0
Due after one year to five years	151
Due after five years to ten years	7,444
Due after ten years	25,011
Total	32,606	$ 32,580
Available-for-sale Securities, Amortized Cost:
Due within one year	836
Due after one year to five years	1,118
Due after five years to ten years	6,150
Due after ten years	33,806
Total	41,910
Available-for-sale Securities, Estimated Fair Value:
Due within one year	834
Due after one year to five years	1,108
Due after five years to ten years	6,160
Due after ten years	33,812
Total	$ 41,914

[1] Derived from audited consolidated financial statements.