Note 3 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Jan. 01, 2022	Dec. 31, 2021
Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,627,000	$ 5,012,000	$ 3,323,000	$ 5,509,000	$ 1,282,000		$ 3,397,000
Retained Earnings [Member]
Equity, Including Portion Attributable to Noncontrolling Interest	(273,539,000)	(271,279,000)	(266,193,000)	(259,521,000)	(256,833,000)		(264,662,000)
Additional Paid-in Capital [Member]
Equity, Including Portion Attributable to Noncontrolling Interest	$ 277,266,000	$ 277,253,000	$ 270,377,000	$ 265,623,000	$ 258,627,000		268,459,000
Accounting Standards Update 2020-06 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Equity, Including Portion Attributable to Noncontrolling Interest							(942,000)
Accounting Standards Update 2020-06 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Convertible Debt [Member]
Debt Instrument, Unamortized Discount						$ 942,000
Accounting Standards Update 2020-06 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member]
Equity, Including Portion Attributable to Noncontrolling Interest						9,739,000	9,739,000
Accounting Standards Update 2020-06 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Additional Paid-in Capital [Member]
Equity, Including Portion Attributable to Noncontrolling Interest						$ 10,681,000	$ (10,681,000)
CAR-TXpress [Member]
Subsidiary, Ownership Percentage, Noncontrolling Owner	20.00%
Subsidiary, Ownership Percentage, Parent	80.00%