Note 5 - Financial Instruments Measured at Fair Value - Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands		Dec. 28, 2024	Dec. 30, 2023
Estimated fair value		$ 55,685	$ 90,174
Corporate Debt Securities [Member]
Estimated fair value	[1]	32,052	45,237
US Treasury Securities [Member]
Estimated fair value		11,961	20,349
Certificates of Deposit [Member]
Estimated fair value		6,972	15,488
Asset-Backed Securities [Member]
Estimated fair value		3,653	8,024
US States and Political Subdivisions Debt Securities [Member]
Estimated fair value		333	335
Debt Security, Government, Non-US [Member]
Estimated fair value		714	741
Fair Value, Recurring [Member]
Assets, Fair Value Disclosure		262,092	335,698
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Estimated fair value		32,052	51,949
Fair Value, Recurring [Member] | US Treasury Securities [Member]
Estimated fair value		11,961	20,349
Fair Value, Recurring [Member] | Certificates of Deposit [Member]
Estimated fair value		6,972	15,488
Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Estimated fair value		3,653	8,024
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Estimated fair value		333	335
Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Estimated fair value		714	741
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure		136,965	157,697
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-Backed Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Security, Government, Non-US [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure		125,127	178,001
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Estimated fair value		32,052	51,949
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Estimated fair value		11,961	20,349
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Estimated fair value		6,972	15,488
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-Backed Securities [Member]
Estimated fair value		3,653	8,024
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Estimated fair value		333	335
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Security, Government, Non-US [Member]
Estimated fair value		714	741
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-Backed Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Security, Government, Non-US [Member]
Estimated fair value		0	0
Fair Value, Recurring [Member] | Cash [Member]
Cash and cash equivalents		136,965	157,697
Fair Value, Recurring [Member] | Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		136,965	157,697
Fair Value, Recurring [Member] | Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents		0	0
Fair Value, Recurring [Member] | Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents		0	0
Fair Value, Recurring [Member] | Money Market Funds [Member]
Cash and cash equivalents		69,442	81,115
Fair Value, Recurring [Member] | Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		0	0
Fair Value, Recurring [Member] | Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents		69,442	81,115
Fair Value, Recurring [Member] | Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents		$ 0	$ 0

[1] 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.