Note 1 - Summary of Significant Accounting Policies - Customer Concentration (Details) - Revenue Benchmark [Member] - Customer Concentration Risk [Member] - Semiconductor Test and Inspection [Member]	9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019
Customers individually accounting for more than 10% of net sales	1	1
One Customer [Member]
Percentage of net sales	11.00%	11.00%