Note 3 - Income Taxes - Deferred Income Taxes (Details) - USD ($)	Sep. 30, 2023	Sep. 30, 2022
Deferred tax assets attributable to:
Accrued liabilities, including supplemental compensation and vacation pay accrual	$ 1,990,000	$ 1,792,000
Impairment losses on marketable securities	(306,000)	(182,000)
Bad debt reserves not yet deductible	55,000	56,000
Depreciation and amortization	2,206,000	2,686,000
Deferred revenues	1,068,000	1,316,000
Goodwill	370,000	451,000
Net operating losses	281,000	657,000
Credits and other	(3,000)	71,000
Total deferred tax assets	5,661,000	6,847,000
Unrealized gains on marketable securities	36,260,000	32,120,000
Net deferred income taxes	$ 30,599,000	$ 25,273,000