Note 4 - Marketable Securities - Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Amortized Cost	$ 98,115	$ 128,196
Unrealized gains	491	147
Unrealized Losses	(5)	(110)
Fair Value	98,601	128,233
Marketable Securities	98,601	128,233
Corporate Debt Securities [Member]
Amortized Cost	55,375	54,256
Unrealized gains	392	74
Unrealized Losses	(1)	(49)
Fair Value	55,766	54,281
Marketable Securities	55,766	54,281
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Amortized Cost	14,285	28,507
Unrealized gains	17	30
Unrealized Losses	0	(3)
Fair Value	14,302	28,534
Marketable Securities	14,302	28,534
Certificates of Deposit [Member]
Amortized Cost	15,711	18,850
Unrealized gains	17	17
Unrealized Losses	0	(1)
Fair Value	15,728	18,866
Marketable Securities	15,728	18,866
US Treasury Securities [Member]
Amortized Cost	4,442	16,127
Unrealized gains	9	3
Unrealized Losses	(3)	(50)
Fair Value	4,448	16,080
Marketable Securities	4,448	16,080
Asset-Backed Securities [Member]
Amortized Cost	8,302	10,456
Unrealized gains	56	23
Unrealized Losses	(1)	(7)
Fair Value	8,357	10,472
Marketable Securities	$ 8,357	$ 10,472