Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Mar. 26, 2022	Dec. 25, 2021
Amortized cost		$ 91,874	$ 89,738
Gross unrealized gains		1	2
Gross unrealized losses	[1]	373	36
Short-term investments		91,502	89,704
Corporate Debt Securities [Member]
Amortized cost	[2]	77,246	84,060
Gross unrealized gains	[2]	1	2
Gross unrealized losses	[1],[2]	292	31
Short-term investments	[2]	76,955	84,031
US Treasury Securities [Member]
Amortized cost		8,713	3,953
Gross unrealized gains		0	0
Gross unrealized losses	[1]	68	5
Short-term investments		8,645	3,948
Certificates of Deposit [Member]
Amortized cost		4,300	800
Gross unrealized gains		0	0
Gross unrealized losses	[1]	10	0
Short-term investments		4,290	800
Debt Security, Government, Non-US [Member]
Amortized cost		884	925
Gross unrealized gains		0	0
Gross unrealized losses	[1]	0	0
Short-term investments		884	$ 925
Asset-Backed Securities [Member]
Amortized cost		731
Gross unrealized gains		0
Gross unrealized losses	[1]	3
Short-term investments		$ 728

[1] As of March 26, 2022 and December 25, 2021, the cost and fair value of investments with loss positions were approximately $85.0 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-thantemporary 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.