Note 3 - Investments- Fair Value of the Company's Investments by Type (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost	$ 9,989	$ 28,211,000
Accrued Interest	65,000	25,000
Gross Unrealized Losses	(13,000)	(3,000)
Total investments	10,041,000	28,239,000
Gross Unrealized Gains		6,000
US Government Agencies Debt Securities [Member]
Amortized Cost	4,043,000	24,986,000
Accrued Interest	17,000	14,000
Gross Unrealized Losses	(7,000)	(3,000)
Total investments	4,053,000	25,000,000
Gross Unrealized Gains		3,000
Corporate Debt Securities [Member]
Amortized Cost	4,294,000
Accrued Interest	40,000
Gross Unrealized Losses	(5,000)
Total investments	4,329,000
Certificates of Deposit [Member]
Amortized Cost	1,652,000	3,225,000
Accrued Interest	8,000	11,000
Gross Unrealized Losses	(1,000)
Total investments	$ 1,659,000	3,239,000
Gross Unrealized Gains		$ 3,000