Note 5 - Fair Value - Summary of Investments in Marketable Securities (Details)	Jan. 01, 2017 USD ($)
Amortized cost	$ 190,876,000
Unrealized gross gains	33,000
Unrealized gross losses	(174,000)
Fair value	190,735,000
US Government Corporations and Agencies Securities [Member]
Amortized cost	21,161,000
Unrealized gross gains	13,000
Unrealized gross losses	(13,000)
Fair value	21,161,000
Corporate Debt Securities [Member]
Amortized cost	97,133
Unrealized gross gains	19
Unrealized gross losses	(159)
Fair value	96,993
US States and Political Subdivisions Debt Securities [Member]
Amortized cost	4,196,000
Unrealized gross gains	1,000
Unrealized gross losses	(2,000)
Fair value	4,195,000
Money Market Funds [Member]
Amortized cost	65,114,000
Unrealized gross gains
Unrealized gross losses
Fair value	65,114,000
Certificates of Deposit [Member]
Amortized cost	3,272,000
Unrealized gross gains
Unrealized gross losses
Fair value	$ 3,272,000

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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