Note 4 - Stock-based Compensation - Summary of Stock-based Compensation by Income Statement Line Item (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 25, 2018	Feb. 26, 2017	Feb. 25, 2018	Feb. 26, 2017
Stock-based compensation expense	$ 1,147	$ 1,069	$ 3,212	$ 2,842
Cost of Sales [Member]
Stock-based compensation expense	137	124	398	361
Research and Development Expense [Member]
Stock-based compensation expense	41	23	82	69
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense	969	922	2,732	2,412
Employee Stock Option [Member]
Stock-based compensation expense	380	308	1,057	907
Restricted Stock Units (RSUs) [Member]
Stock-based compensation expense	$ 762	$ 761	$ 2,155	$ 1,935