Note 3 - Stock-based Compensation - Summary of Stock-based Compensation by Income Statement Line Item (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Feb. 26, 2017	Feb. 28, 2016	Feb. 26, 2017	Feb. 28, 2016
Stock-based Compensation Expense	$ 1,069	$ 884	$ 2,842	$ 2,581
Cost of Sales [Member]
Stock-based Compensation Expense	124	103	361	301
Research and Development Expense [Member]
Stock-based Compensation Expense	23	22	69	67
Selling, General and Administrative Expenses [Member]
Stock-based Compensation Expense	922	759	2,412	2,213
Employee Stock Option [Member]
Stock-based Compensation Expense	308	331	907	1,021
Restricted Stock Units (RSUs) [Member]
Stock-based Compensation Expense	$ 761	$ 553	$ 1,935	$ 1,560

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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