Note 3 - Investment Securities (Tables)

3 Months Ended

Mar. 31, 2024

Notes Tables

Debt Securities, Held-to-Maturity [Table Text Block]

	March 31, 2024
	Amortized		Gross		Gross
	cost, as		unrealized		unrealized		Estimated
(in thousands)	adjusted		holding gains		holding losses		fair value
Short-term investments:
Obligations of domestic governmental agencies (maturing between April 2024 and September 2024) (held-to-maturity)	$	134,308	$	—	$	28	$	134,280
Total short-term investments	$	134,308	$	—	$	28	$	134,280

	December 31, 2023
	Amortized		Gross		Gross
	cost, as		unrealized		unrealized		Estimated
	adjusted		holding gains		holding losses		fair value
Short-term investments:
Obligations of domestic governmental agencies (maturing between January 2024 and June 2024) (held-to-maturity)	$	124,575	$	30	$	53	$	124,552
Total short-term investments	$	124,575	$	30	$	53	$	124,552