Note 3 - Income Taxes - Deferred Income Taxes (Details) - USD ($)	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Deferred tax assets attributable to:
Accrued liabilities, including supplemental compensation and vacation pay accrual	$ (69,000)	$ 455,000	$ 605,000
Impairment losses on investments	1,376,000	1,382,000	1,369,000
Bad debt reserves not yet deductible	62,000	62,000	82,000
Depreciation and amortization	5,977,000	4,549,000	3,251,000
Deferred revenues	1,431,000	1,555,000	1,378,000
Credits and other	4,403,000	1,519,000	869,000
Total deferred tax assets	13,180,000	9,522,000	7,554,000
Deferred tax liabilities attributable to:
Unrealized gains on investments	(64,550,000)	(42,250,000)	(43,278,000)
Goodwill	(311,000)	(1,227,000)	(896,000)
Total deferred tax liabilities	(64,861,000)	(43,477,000)	(44,174,000)
Net deferred income taxes	$ (51,681,000)	$ (33,955,000)	$ (36,620,000)