Condensed Consolidated Statements of Shareholders' Equity - USD ($)	Total	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Common Stock [Member]	Class B Stock [Member]
Beginning balance at Sep. 30, 2019	$ 155,515,000	$ 12,159,000	$ 141,897,000	$ 1,228,000	$ 231,000
Beginning balance, shares at Sep. 30, 2019				12,277,337	2,308,857
Net income	2,489,000		2,489,000
Stock-based compensation	18,000	18,000
Ending balance at Dec. 31, 2019	158,022,000	12,177,000	144,386,000	$ 1,228,000	$ 231,000
Ending balance, shares at Dec. 31, 2019				12,277,337	2,308,857
Beginning balance at Sep. 30, 2020	161,220,000	12,331,000	147,428,000	$ 1,229,000	$ 232,000
Beginning balance, shares at Sep. 30, 2020				12,287,337	2,318,857
Net income	1,551,000		1,551,000
Ending balance at Dec. 31, 2020	$ 162,771,000	$ 12,331,000	$ 148,979,000	$ 1,229,000	$ 232,000
Ending balance, shares at Dec. 31, 2020				12,287,337	2,318,857