Note 3 - Fair Value Measurements - Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Mar. 31, 2023 | Dec. 31, 2022 |
Marketable Securities | $ 148,143 | $ 151,663 |
Corporate Debt Securities [Member] | | |
Marketable Securities | 51,959 | 87,760 |
Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | | |
Marketable Securities | 49,676 | 37,682 |
Certificates of Deposit [Member] | | |
Marketable Securities | 26,807 | 19,667 |
US Treasury Securities [Member] | | |
Marketable Securities | 11,523 | |
Asset-Backed Securities [Member] | | |
Marketable Securities | 8,178 | 6,554 |
Fair Value, Recurring [Member] | | |
Total assets | 149,137 | 161,101 |
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | | |
Marketable Securities | 51,959 | 87,760 |
Fair Value, Recurring [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | | |
Marketable Securities | 49,676 | 37,682 |
Fair Value, Recurring [Member] | Certificates of Deposit [Member] | | |
Marketable Securities | 26,807 | 19,667 |
Fair Value, Recurring [Member] | US Treasury Securities [Member] | | |
Marketable Securities | 11,523 | |
Fair Value, Recurring [Member] | Asset-Backed Securities [Member] | | |
Marketable Securities | 8,178 | 6,554 |
Fair Value, Recurring [Member] | Cash and Cash Equivalents [Member] | | |
Marketable Securities | 994 | 9,438 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Total assets | 62,193 | 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 | 49,676 | 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] | US Treasury Securities [Member] | | |
Marketable Securities | 11,523 | |
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 | 994 | 9,438 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Total assets | 86,944 | 113,981 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member] | | |
Marketable Securities | 51,959 | 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 | 0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member] | | |
Marketable Securities | 26,807 | 19,667 |
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 2 [Member] | Asset-Backed Securities [Member] | | |
Marketable Securities | 8,178 | 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 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] | US Treasury Securities [Member] | | |
Marketable Securities | 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 |