Note 4 - Fair Value Measurements - Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities	$ 128,233	$ 151,663
Corporate Debt Securities [Member]
Marketable Securities	54,281	87,760
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	28,534	37,682
Certificates of Deposit [Member]
Marketable Securities	18,866	19,667
Asset-Backed Securities [Member]
Marketable Securities	10,472	6,554
US Treasury Securities [Member]
Marketable Securities	16,080
Fair Value, Recurring [Member]
Total assets	128,808	161,101
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Marketable Securities	54,281	87,760
Fair Value, Recurring [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	28,534	37,682
Fair Value, Recurring [Member] | Certificates of Deposit [Member]
Marketable Securities	18,866	19,667
Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Marketable Securities	10,472	6,554
Fair Value, Recurring [Member] | Cash and Cash Equivalents [Member]
Marketable Securities	575	9,438
Fair Value, Recurring [Member] | US Treasury Securities [Member]
Marketable Securities	16,080
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total assets	45,189	47,120
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	28,534	37,682
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] | Asset-Backed Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Marketable Securities	575	9,438
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Marketable Securities	16,080
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total assets	83,619	113,981
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Marketable Securities	54,281	87,760
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Marketable Securities	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Marketable Securities	18,866	19,667
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-Backed Securities [Member]
Marketable Securities	10,472	6,554
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Marketable Securities	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
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] | Asset-Backed Securities [Member]
Marketable Securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Marketable Securities	0	$ 0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Marketable Securities	$ 0