Note 3 - Fair Value Measurements - Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Marketable Securities	$ 132,581	$ 128,233
Corporate Debt Securities [Member]
Marketable Securities	61,914	54,281
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	30,124	28,534
Certificates of Deposit [Member]
Marketable Securities	17,943	18,866
US Treasury Securities [Member]
Marketable Securities	12,658	16,080
Asset-Backed Securities [Member]
Marketable Securities	9,942	10,472
Fair Value, Recurring [Member]
Cash equivalents	1,549	575
Total assets	134,130	128,808
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Marketable Securities	61,914	54,281
Fair Value, Recurring [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	30,124	28,534
Fair Value, Recurring [Member] | Certificates of Deposit [Member]
Marketable Securities	17,943	18,866
Fair Value, Recurring [Member] | US Treasury Securities [Member]
Marketable Securities	12,658	16,080
Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Marketable Securities	9,942	10,472
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents	1,549	575
Total assets	44,331	45,189
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	30,124	28,534
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Marketable Securities	12,658	16,080
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-Backed Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents	0	0
Total assets	89,799	83,619
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Marketable Securities	61,914	54,281
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Marketable Securities	17,943	18,866
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-Backed Securities [Member]
Marketable Securities	9,942	10,472
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents	0	0
Total assets	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-Backed Securities [Member]
Marketable Securities	$ 0	$ 0