Note 1 - Description of Business and Summary of Significant Accounting Policies - Summary of Fair Value Hierarchy for Financial Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Assets, fair value	$ 50,396
Fair Value, Recurring [Member]
Assets, fair value	50,396	$ 30,307
Fair Value, Recurring [Member] | Money Market Securities [Member]
Assets, fair value	2,073	2,478
Fair Value, Recurring [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Assets, fair value	35,468	13,382
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Assets, fair value	4,423	9,585
Fair Value, Recurring [Member] | Federal Agency Notes [Member]
Assets, fair value	8,432	3,799
Fair Value, Recurring [Member] | Pre-funded Municipals [Member]
Assets, fair value	0	1,063
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value	2,073	2,478
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Securities [Member]
Assets, fair value	2,073	2,478
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Federal Agency Notes [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Pre-funded Municipals [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value	48,323	27,829
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Securities [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Assets, fair value	35,468	13,382
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Assets, fair value	4,423	9,585
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Federal Agency Notes [Member]
Assets, fair value	8,432	3,799
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Pre-funded Municipals [Member]
Assets, fair value	0	1,063
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Securities [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Federal Agency Notes [Member]
Assets, fair value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Pre-funded Municipals [Member]
Assets, fair value	$ 0	$ 0