Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Dec. 31, 2022	Dec. 25, 2021
Amortized cost		$ 143,952	$ 89,738
Gross unrealized gains		61	2
Gross unrealized losses	[1]	778	36
Short-term investments		143,235	89,704
Corporate Debt Securities [Member]
Amortized cost	[2]	59,283	84,060
Gross unrealized gains	[2]	30	2
Gross unrealized losses	[1],[2]	240	31
Short-term investments	[2]	59,073	84,031
US Treasury Securities [Member]
Amortized cost		34,614	3,953
Gross unrealized gains		1	0
Gross unrealized losses	[1]	418	5
Short-term investments		34,197	3,948
Certificates of Deposit [Member]
Amortized cost		36,500	800
Gross unrealized gains		20	0
Gross unrealized losses	[1]	41	0
Short-term investments		36,479	800
Asset-Backed Securities [Member]
Amortized cost		12,727
Gross unrealized gains		10
Gross unrealized losses		79
Short-term investments		12,658
Debt Security, Government, Non-US [Member]
Amortized cost		828	925
Gross unrealized gains		0	0
Gross unrealized losses	[1]	0	0
Short-term investments		$ 828	$ 925

[1] As of December 31, 2022, the cost and fair value of investments with loss positions were approximately $86.3 million and $85.5 million, respectively. As of December 25, 2021, the cost and fair value of investments with loss positions was approximately $57.0 million. We evaluated the nature of these investments, credit worthiness of the issuer and the duration of these impairments to determine if an other-than-temporary decline in fair value had occurred and concluded that these losses were temporary and 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.