Note 7 - Stockholders' Equity (Details Textual) - USD ($)	1 Months Ended	3 Months Ended						8 Months Ended	9 Months Ended		18 Months Ended
	Mar. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2021	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Feb. 25, 2022	Feb. 24, 2022
Statement [Line Items]
Payments for Repurchase of Common Stock									$ 938,000	$ 233,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)		0			0				0	0
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period (in shares)		0			0				2,000	0
Share-Based Payment Arrangement, Expense		$ 0			$ 0				$ 0	$ 733,000
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 0	$ 0			$ 0				$ 0	$ 0	$ 0
Plan1989 [Member]
Statement [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)	229,000	229,000			231,000				229,000	231,000	229,000
Treasury Stock, Common [Member]
Statement [Line Items]
Treasury Stock, Shares, Acquired (in shares)		193,040	87,407	39,965	19,487	10,457	13,647
Common Class A [Member] | Plan1989 [Member]
Statement [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share)	$ 6.05	$ 6.05			$ 6.05				$ 6.05	$ 6.05	$ 6.05
Common Class A [Member] | Plan1997 [Member]
Statement [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)	2,000	2,000			2,000				2,000	2,000	2,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share)	$ 2.74	$ 2.74			$ 2.74				$ 2.74	$ 2.74	$ 2.74
Common Class A [Member] | Treasury Stock, Common [Member]
Statement [Line Items]
Treasury Stock, Shares, Acquired (in shares)		193,040			19,487				320,412	43,591
Payments for Repurchase of Common Stock		$ 556,000			$ 97,000				$ 938,000	$ 233,000
Share Repurchase Plan Renewal December2012 December2020 [Member]
Statement [Line Items]
Stock Repurchase Program, Authorized Amount	$ 5,000,000.0	$ 5,000,000.0							$ 5,000,000.0		$ 5,000,000.0	$ 5,000,000.0	$ 2,750,000
Monthly Dividends Paid [Member]
Statement [Line Items]
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 0.0075							$ 0.0050			$ 0.0075