Note 3 - Income Taxes - Operating Loss Carryforwards (Details) $ in Millions	Sep. 30, 2020 USD ($)
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforward	$ 20.1
Operating Loss Carryforward, No Expiration	1.6
Domestic Tax Authority [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforward	6.1
Domestic Tax Authority [Member] | Other State [Member]
Operating Loss Carryforward	2.6
Domestic Tax Authority [Member] | Expires at Fiscal Year Ended September 30, 2036 [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforward	8.0
Domestic Tax Authority [Member] | Expires at Fiscal Year Ended September 30, 2037 [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforward	6.6
Domestic Tax Authority [Member] | Expires at Fiscal Year Ended September 30, 2038 [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforward	11.1
Domestic Tax Authority [Member] | Expires at Fiscal Year Ended September 30, 2039 [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforward	0.0
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforward, No Expiration	0.0
State and Local Jurisdiction [Member] | Other State [Member]
Operating Loss Carryforward, No Expiration	0.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2036 [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforward	0.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2036 [Member] | Other State [Member]
Operating Loss Carryforward	0.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2037 [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforward	0.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2037 [Member] | Other State [Member]
Operating Loss Carryforward	3.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2038 [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforward	5.4
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2038 [Member] | Other State [Member]
Operating Loss Carryforward	2.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2039 [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforward	7.0
State and Local Jurisdiction [Member] | Expires at Fiscal Year Ended September 30, 2039 [Member] | Other State [Member]
Operating Loss Carryforward	$ 3.0