Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Dec. 31, 2022
Amortized cost		$ 94,536	$ 143,952
Gross unrealized gains		8	61
Gross unrealized losses	[1]	364	778
Short-term investments		94,180	143,235
Corporate Debt Securities [Member]
Amortized cost	[2]	40,601	59,283
Gross unrealized gains	[2]	2	30
Gross unrealized losses	[1],[2]	75	240
Short-term investments	[2]	40,528	59,073
Certificates of Deposit [Member]
Amortized cost		22,640	36,500
Gross unrealized gains		6	20
Gross unrealized losses	[1]	7	41
Short-term investments		22,639	36,479
US Treasury Securities [Member]
Amortized cost		21,918	34,614
Gross unrealized gains		0	1
Gross unrealized losses	[1]	251	418
Short-term investments		21,667	34,197
Asset-Backed Securities [Member]
Amortized cost		8,652	12,727
Gross unrealized gains		0	10
Gross unrealized losses	[1]	31	79
Short-term investments		8,621	12,658
Debt Security, Government, Non-US [Member]
Amortized cost		725	828
Gross unrealized gains		0	0
Gross unrealized losses	[1]	0	0
Short-term investments		$ 725	$ 828

[1] As of September 30, 2023, the cost and fair value of investments with loss positions was approximately $75.8 million and $75.4 million, respectively. As of December 31, 2022, the cost and fair value of investments with loss positions was approximately $86.3 million and $85.5 million, respectively. We evaluated the nature of these investments, credit worthiness of the issuer and the duration of these impairments to determine if a credit loss exists. We have the ability and intent to hold these investments to maturity.

[2] Corporate debt securities include investments in financial and other corporate institutions. No single issuer represents a significant portion of the total corporate debt securities portfolio.