Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Sep. 30, 2018	$ 79,583,112	$ 39,973,075	$ 13,043,656	$ 27,438,049	$ (871,668)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,698,412			8,698,412
Other comprehensive loss	(1,617,249)				(1,617,249)
Exercise of stock options	412,179	157,540	254,639
Cash dividends declared	(5,314,544)			(5,314,544)
Issuance of common stock	1,334,482	235,705	1,098,777
Ending balance at Sep. 30, 2019	83,096,392	40,366,320	14,397,072	30,821,917	(2,488,917)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,564,534			10,564,534
Other comprehensive loss	(959,027)				(959,027)
Exercise of stock options	439,508	149,960	289,548
Stock option grants	81,380		81,380
Cash dividends declared	(5,697,941)			(5,697,941)
Issuance costs	(147,517)		(147,517)
Issuance of common stock	1,510,648	284,010	1,226,638
Ending balance at Sep. 30, 2020	$ 88,887,977	$ 40,800,290	$ 15,847,121	$ 35,688,510	$ (3,447,944)