Note 4 - Marketable Securities - Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Amortized Cost	$ 126,914	$ 128,196
Unrealized gains	67	147
Unrealized Losses	(158)	(110)
Fair Value	126,823	128,233
Marketable Securities	126,823	128,233
Corporate Debt Securities [Member]
Amortized Cost	63,135	54,256
Unrealized gains	43	74
Unrealized Losses	(77)	(49)
Fair Value	63,101	54,281
Marketable Securities	63,101	54,281
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Amortized Cost	24,217	28,507
Unrealized gains	0	30
Unrealized Losses	(13)	(3)
Fair Value	24,204	28,534
Marketable Securities	24,204	28,534
Certificates of Deposit [Member]
Amortized Cost	17,068	18,850
Unrealized gains	10	17
Unrealized Losses	(2)	(1)
Fair Value	17,076	18,866
Marketable Securities	17,076	18,866
US Treasury Securities [Member]
Amortized Cost	12,792	16,127
Unrealized gains	0	3
Unrealized Losses	(64)	(50)
Fair Value	12,728	16,080
Marketable Securities	12,728	16,080
Asset-Backed Securities [Member]
Amortized Cost	9,702	10,456
Unrealized gains	14	23
Unrealized Losses	(2)	(7)
Fair Value	9,714	10,472
Marketable Securities	$ 9,714	$ 10,472