Note 3 - Accounting Standards Adopted in Fiscal 2019 and Recent Accounting Pronouncements (Details Textual) - USD ($)	3 Months Ended				6 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Net Income (Loss) Attributable to Parent, Total	$ 5,018,000	$ (21,533,000)	$ (232,000)	$ 14,739,000	$ (16,515,000)	$ 14,507,000
Unrealized Gain (Loss) on Investments, Total	8,497,000				$ (20,143,000)
Cumulative Effect of New Accounting Principle in Period of Adoption
AOCI Attributable to Parent [Member]
Net Income (Loss) Attributable to Parent, Total
Cumulative Effect of New Accounting Principle in Period of Adoption								(115,786,000)
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent, Total	$ 5,018,000	$ (21,533,000)	$ (232,000)	$ 14,739,000
Cumulative Effect of New Accounting Principle in Period of Adoption								$ 115,786,000
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption							$ (115,786,000)
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption							$ 115,786,000