Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at beginning of period 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	2,434,162			2,434,162
Other comprehensive income (loss)	(83,316)				(83,316)
Cash dividends declared	(1,322,335)			(1,322,335)
Issuance of common stock	348,117	85,175	262,942
Balance at end of period at Dec. 31, 2018	80,959,740	40,058,250	13,306,598	28,549,876	(954,984)
Balance at beginning of period 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	8,242,807
Other comprehensive income (loss)	(589,162)
Balance at end of period at Jun. 30, 2019	84,736,935	40,319,785	14,179,376	31,698,604	(1,460,830)
Balance at beginning of period at Dec. 31, 2018	80,959,740	40,058,250	13,306,598	28,549,876	(954,984)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,670,090			4,670,090
Other comprehensive income (loss)	(46,034)				(46,034)
Cash dividends declared	(1,329,178)			(1,329,178)
Issuance of common stock	719,899	158,110	561,789
Balance at end of period at Mar. 31, 2019	84,974,517	40,216,360	13,868,387	31,890,788	(1,001,018)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,138,555			1,138,555
Other comprehensive income (loss)	(459,812)				(459,812)
Cash dividends declared	(1,330,739)			(1,330,739)
Issuance of common stock	414,414	103,425	310,989
Balance at end of period at Jun. 30, 2019	84,736,935	40,319,785	14,179,376	31,698,604	(1,460,830)
Balance at beginning of period 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	4,006,936			4,006,936
Other comprehensive income (loss)	279,844				279,844
Cash dividends declared	(1,419,236)			(1,419,236)
Issuance of common stock	395,199	90,265	304,934
Balance at end of period at Dec. 31, 2019	86,359,135	40,456,585	14,702,006	33,409,617	(2,209,073)
Balance at beginning of period 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	10,893,830
Other comprehensive income (loss)	(1,029,948)
Balance at end of period at Jun. 30, 2020	90,251,152	40,737,185	15,586,761	37,446,071	(3,518,865)
Balance at beginning of period at Dec. 31, 2019	86,359,135	40,456,585	14,702,006	33,409,617	(2,209,073)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,680,316			5,680,316
Other comprehensive income (loss)	(1,199,783)				(1,199,783)
Cash dividends declared	(1,424,192)			(1,424,192)
Issuance of common stock	901,871	228,140	673,731
Balance at end of period at Mar. 31, 2020	90,317,347	40,684,725	15,375,737	37,665,741	(3,408,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,206,578			1,206,578
Other comprehensive income (loss)	(110,009)				(110,009)
Stock option grants	40,692		40,692
Cash dividends declared	(1,426,248)			(1,426,248)
Issuance of common stock	222,792	52,460	170,332
Balance at end of period at Jun. 30, 2020	$ 90,251,152	$ 40,737,185	$ 15,586,761	$ 37,446,071	$ (3,518,865)