Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Jun. 25, 2022	Dec. 25, 2021
Amortized cost		$ 88,028	$ 89,738
Gross unrealized gains		4	2
Gross unrealized losses	[1]	537	36
Short-term investments		87,495	89,704
Corporate Debt Securities [Member]
Amortized cost	[2]	63,577	84,060
Gross unrealized gains	[2]	3	2
Gross unrealized losses	[1],[2]	365	31
Short-term investments	[2]	63,215	84,031
US Treasury Securities [Member]
Amortized cost		8,722	3,953
Gross unrealized gains		0	0
Gross unrealized losses	[1]	105	5
Short-term investments		8,617	3,948
Certificates of Deposit [Member]
Amortized cost		10,750	800
Gross unrealized gains		1	0
Gross unrealized losses	[1]	32	0
Short-term investments		10,719	800
Debt Security, Government, Non-US [Member]
Amortized cost		841	925
Gross unrealized gains		0	0
Gross unrealized losses	[1]	0	0
Short-term investments		841	$ 925
Asset-Backed Securities [Member]
Amortized cost		4,138
Gross unrealized gains		0
Gross unrealized losses	[1]	35
Short-term investments		$ 4,103

[1] As of June 25, 2022 and December 25, 2021, the cost and fair value of investments with loss positions were approximately $79.7 million and $57.0 million, respectively. 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.