Note 1 - Description of Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

December 31, 2022	Level 1		Level 2		Level 3		Total
Money market securities	$	2,073	$	—	$	—	$	2,073
Commercial paper		—		35,468		—		35,468
Federal agency notes		—		8,432		—		8,432
Corporate notes		—		4,423		—		4,423
Pre-refunded municipals		—		—		—		—
Total	$	2,073	$	48,323	$	—	$	50,396

December 31, 2021	Level 1		Level 2		Level 3		Total
Money market securities	$	2,478	$	—	$	—	$	2,478
Commercial paper		—		13,382		—		13,382
Corporate notes		—		9,585		—		9,585
Federal agency notes		—		3,799		—		3,799
Pre-refunded municipals		—		1,063		—		1,063
Total	$	2,478	$	27,829	$	—	$	30,307

Investments Classified by Contractual Maturity Date [Table Text Block]

	Maturities by Period
			Less than		1-5		5-10		More than
	Total		1 year		years		years		10 years
Cash equivalents and marketable securities	$	50,396	$	50,396	$	—	$	—	$	—