Note 3 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Jan. 01, 2022	Dec. 31, 2021
Equity, Including Portion Attributable to Noncontrolling Interest	$ 3,263,000	$ 2,627,000	$ 5,012,000	$ 3,323,000	$ 4,266,000	$ 5,509,000	$ 1,282,000		$ 3,397,000
Retained Earnings [Member]
Equity, Including Portion Attributable to Noncontrolling Interest	(277,154,000)	(273,539,000)	(271,279,000)	(266,193,000)	(262,761,000)	(259,521,000)	(256,833,000)		(264,662,000)
Additional Paid-in Capital [Member]
Equity, Including Portion Attributable to Noncontrolling Interest	$ 281,632,000	$ 277,266,000	$ 277,253,000	$ 270,377,000	$ 267,761,000	$ 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%