Note 7 - Fair Value Measurements - Fair Value of Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Marketable securities	$ 54,510
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities	17,096	$ 7,602
Total	76,457	73,531
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash [Member]
Cash	36,813	65,637
Cash and cash equivalents	36,813	65,637
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Cash	22,548	292
Cash and cash equivalents	22,548	292
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities	37,414	18,318
Total	37,414	18,318
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash [Member]
Cash	0	0
Cash and cash equivalents	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Cash	0	0
Cash and cash equivalents	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities	0	0
Total	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash [Member]
Cash	0	0
Cash and cash equivalents	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Cash	0	0
Cash and cash equivalents	$ 0	$ 0