Note 10 - Income Taxes - Net Operating Loss Carryforwards Arrangement (Details) $ in Millions	Dec. 31, 2021 USD ($)
Domestic Tax Authority [Member]
Operating loss carryforward subject to expiration	$ 74.1
Operating loss carryforward not subject to expiration	36.7
Operating loss carryforward, total	110.7
Domestic Tax Authority [Member] | Tax Year 2025 [Member]
Operating loss carryforward subject to expiration	4.2
Domestic Tax Authority [Member] | Tax Year 2028 [Member]
Operating loss carryforward subject to expiration	5.2
Domestic Tax Authority [Member] | Tax Year 2026 [Member]
Operating loss carryforward subject to expiration	25.5
Domestic Tax Authority [Member] | Tax Year 2029 [Member]
Operating loss carryforward subject to expiration	7.7
Domestic Tax Authority [Member] | Tax Year 2027 [Member]
Operating loss carryforward subject to expiration	15.5
Domestic Tax Authority [Member] | Tax Year 2030 [Member]
Operating loss carryforward subject to expiration	10.6
Domestic Tax Authority [Member] | Tax Year 2034 [Member]
Operating loss carryforward subject to expiration	2.5
Domestic Tax Authority [Member] | Tax Year 2035 [Member]
Operating loss carryforward subject to expiration	1.5
Domestic Tax Authority [Member] | Tax Year 2031 [Member]
Operating loss carryforward subject to expiration	1.3
Domestic Tax Authority [Member] | Tax Year 2032 [Member]
Operating loss carryforward subject to expiration	0.0
Domestic Tax Authority [Member] | Tax Year 2033 [Member]
Operating loss carryforward subject to expiration	0.1
State and Local Jurisdiction [Member]
Operating loss carryforward subject to expiration	0.8
Operating loss carryforward, total	55.7
State and Local Jurisdiction [Member] | CALIFORNIA
Operating loss carryforward subject to expiration	27.6
State and Local Jurisdiction [Member] | Other State [Member]
Operating loss carryforward subject to expiration	28.1
State and Local Jurisdiction [Member] | Tax Year 2028 [Member]
Operating loss carryforward subject to expiration	2.6
State and Local Jurisdiction [Member] | Tax Year 2029 [Member]
Operating loss carryforward subject to expiration	5.8
State and Local Jurisdiction [Member] | Tax Year 2030 [Member]
Operating loss carryforward subject to expiration	11.0
State and Local Jurisdiction [Member] | Tax Year 2034 [Member]
Operating loss carryforward subject to expiration	1.4
State and Local Jurisdiction [Member] | Tax Year 2035 [Member]
Operating loss carryforward subject to expiration	0.8
State and Local Jurisdiction [Member] | Tax Year 2038 [Member]
Operating loss carryforward subject to expiration	2.3
State and Local Jurisdiction [Member] | Tax Year 2039 [Member]
Operating loss carryforward subject to expiration	2.2
State and Local Jurisdiction [Member] | Tax Year 2040 [Member]
Operating loss carryforward subject to expiration	$ 0.6