Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	2018 Dividend Reinvestment And Stock Purchase Plan [Member]	2021 Dividend Reinvestment And Stock Purchase Plan [Member]	Common Stock [Member]	Common Stock [Member] 2018 Dividend Reinvestment And Stock Purchase Plan [Member]	Common Stock [Member] 2021 Dividend Reinvestment And Stock Purchase Plan [Member]	Retained Earnings [Member]
Beginning balance at Sep. 30, 2019	$ 75,528			$ 17,673			$ 57,855
Beginning balance, Shares at Sep. 30, 2019				7,527,040
Net income	2,628						2,628
Dividends declared	(1,032)						(1,032)
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		$ 20			$ 20
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					1,702
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		18			$ 18
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					1,596
Stock-based compensation	447			$ 447
Shares repurchased pursuant to stock buyback program	(685)			$ (128)			(557)
Shares repurchased pursuant to stock buyback program, Shares				(64,787)
Ending balance at Dec. 31, 2019	76,924			$ 18,030			58,894
Ending balance, shares at Dec. 31, 2019				7,465,551
Beginning balance at Sep. 30, 2019	75,528			$ 17,673			57,855
Beginning balance, Shares at Sep. 30, 2019				7,527,040
Net income	6,373
Ending balance at Jun. 30, 2020	77,565			$ 18,557			59,008
Ending balance, shares at Jun. 30, 2020				7,263,781
Beginning balance at Dec. 31, 2019	76,924			$ 18,030			58,894
Beginning balance, Shares at Dec. 31, 2019				7,465,551
Net income	1,970						1,970
Dividends declared	(1,011)						(1,011)
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					46
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		18			$ 18
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					1,835
Stock-based compensation	447			$ 447
Shares repurchased pursuant to stock buyback program	(2,028)			$ (406)			(1,622)
Shares repurchased pursuant to stock buyback program, Shares				(206,109)
Ending balance at Mar. 31, 2020	76,320			$ 18,089			58,231
Ending balance, shares at Mar. 31, 2020				7,261,323
Net income	1,775						1,775
Dividends declared	(998)						(998)
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		2			$ 2
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					187
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		19			$ 19
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					2,271
Stock-based compensation	447			$ 447
Ending balance at Jun. 30, 2020	77,565			$ 18,557			59,008
Ending balance, shares at Jun. 30, 2020				7,263,781
Beginning balance at Sep. 30, 2020	78,178			$ 18,705			59,473
Beginning balance, Shares at Sep. 30, 2020				7,356,822
Net income	1,773						1,773
Dividends declared	(1,011)						(1,011)
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		6			$ 6
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					652
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		19			$ 19
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					2,165
Stock-based compensation	352			$ 352
Ending balance at Dec. 31, 2020	79,317			$ 19,082			60,235
Ending balance, shares at Dec. 31, 2020				7,359,639
Beginning balance at Sep. 30, 2020	78,178			$ 18,705			59,473
Beginning balance, Shares at Sep. 30, 2020				7,356,822
Net income	5,903
Ending balance at Jun. 30, 2021	82,186			$ 19,846			62,340
Ending balance, shares at Jun. 30, 2021				7,366,649
Beginning balance at Dec. 31, 2020	79,317			$ 19,082			60,235
Beginning balance, Shares at Dec. 31, 2020				7,359,639
Net income	1,886						1,886
Dividends declared	(1,012)						(1,012)
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan		$ 3	$ 7		$ 3	$ 7
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares					306	838
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan			19			$ 19
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares						2,298
Stock-based compensation	351			$ 351
Ending balance at Mar. 31, 2021	80,571			$ 19,462			61,109
Ending balance, shares at Mar. 31, 2021				7,363,081
Net income	2,244						2,244
Dividends declared	(1,013)						(1,013)
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan			13			$ 13
Shares issued for auto-investments pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares						1,424
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan			$ 20			$ 20
Shares issued for dividend reinvestment pursuant to the 2018 Dividend Reinvestment and Stock Purchase Plan, Shares						2,144
Stock-based compensation	351			$ 351
Ending balance at Jun. 30, 2021	$ 82,186			$ 19,846			$ 62,340
Ending balance, shares at Jun. 30, 2021				7,366,649