Note 3 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands		Jun. 24, 2017	Dec. 31, 2016
Gross Unrealized Gains		$ 1	$ 2
Gross Unrealized Losses	[1]	5	7
Short-term investments		21,810	31,990	[2]
Amortized Cost		21,814	31,995
Corporate Debt Securities [Member]
Gross Unrealized Gains	[3]	1	1
Gross Unrealized Losses	[1],[3]	4	6
Short-term investments	[3]	13,704	22,508
Amortized Cost	[3]	13,707	22,513
US Government-sponsored Enterprises Debt Securities [Member]
Gross Unrealized Gains
Gross Unrealized Losses	[1]		1
Short-term investments		1,000	8,108
Amortized Cost		1,000	8,109
US Treasury Securities [Member]
Gross Unrealized Gains
Gross Unrealized Losses	[1]	1
Short-term investments		5,196
Amortized Cost		5,197
Certificates of Deposit [Member]
Gross Unrealized Gains			1
Gross Unrealized Losses	[1]
Short-term investments		1,294	751
Amortized Cost		1,294	750
Foreign Government Debt Securities [Member]
Gross Unrealized Gains
Gross Unrealized Losses	[1]
Short-term investments		616	623
Amortized Cost		$ 616	$ 623

[1] As of June 24, 2017 there were $16.6 million of investments in our portfolio in a loss position. As of December 31, 2016 the cost and fair value of investments with loss positions were approximately $26.6 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 31, 2016 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.