Note 3 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Sep. 29, 2018	Dec. 30, 2017
Amortized Cost			$ 21,338
Gross Unrealized Gains			1
Gross Unrealized Losses	[1]		10
Short-term investments		$ 549	21,329	[2]
Debt Security, Government, Non-US [Member]
Amortized Cost		549	619
Gross Unrealized Gains
Gross Unrealized Losses	[1]
Short-term investments		$ 549	619
Corporate Debt Securities [Member]
Amortized Cost	[3]		12,784
Gross Unrealized Gains	[3]		1
Gross Unrealized Losses	[1],[3]		6
Short-term investments	[3]		12,779
US Treasury Securities [Member]
Amortized Cost			7,935
Gross Unrealized Gains
Gross Unrealized Losses	[1]		4
Short-term investments			$ 7,931

[1] As of September 29, 2018, there were no investments in our portfolio in a loss position. As of December 30, 2017, the cost and fair value of investments with loss positions were approximately $13.2 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] Derived from December 30, 2017 audited financial statements

[3] 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.