Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Sep. 24, 2022	Dec. 25, 2021
Amortized cost		$ 137,886	$ 89,738
Gross unrealized gains		15	2
Gross unrealized losses	[1]	918	36
Short-term investments		136,983	89,704
Corporate Debt Securities [Member]
Amortized cost	[2]	72,632	84,060
Gross unrealized gains	[2]	6	2
Gross unrealized losses	[1],[2]	371	31
Short-term investments	[2]	72,267	84,031
US Treasury Securities [Member]
Amortized cost		32,522	3,953
Gross unrealized gains		0	0
Gross unrealized losses	[1]	422	5
Short-term investments		32,100	3,948
Certificates of Deposit [Member]
Amortized cost		23,325	800
Gross unrealized gains		9	0
Gross unrealized losses	[1]	51	0
Short-term investments		23,283	800
Debt Security, Government, Non-US [Member]
Amortized cost		783	925
Gross unrealized gains		0	0
Gross unrealized losses	[1]	0	0
Short-term investments		783	$ 925
Asset-Backed Securities [Member]
Amortized cost		8,624
Gross unrealized gains		0
Gross unrealized losses	[1]	74
Short-term investments		$ 8,550

[1] As of September 24, 2022, the cost and fair value of investments with loss positions was approximately $119.3 million and $118.4 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.