Note 6 - Employee Benefit Plans (Details Textual) - USD ($)		12 Months Ended
	May 08, 2019	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay		8.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount		$ 2,000,000	$ 1,100,000	$ 600,000
Deferred Compensation Liability, Current, Total		2,000,000	2,000,000
Cash Surrender Value of Life Insurance		$ 1,700,000	$ 1,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		0	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value		$ 200,000	$ 900,000	$ 10,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value		4,400,000
Share-based Payment Arrangement, Expense		$ 14,148,000	$ 10,053,000	$ 7,007,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		694,000	822,000	353,000
Restricted Stock Units (RSUs) [Member] | Xcerra Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period			529,995
Restricted Stock Units (RSUs) [Member] | Executive Officers and Board of Directors of Xcerra [Member]
Share-based Payment Arrangement, Expense			$ 8,200,000
Restricted Stock Units (RSUs) [Member] | Vesting Over One Year Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			1 year
Restricted Stock Units (RSUs) [Member] | Vesting Over Two Year Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			2 years
Restricted Stock Units (RSUs) [Member] | Vesting Over Four Year Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			4 years
Equity Based Performance Stock Units Granted in 2019, 2018, 2017, and 2016 [Member] | Vest on the Third Anniversary of Awards Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage			100.00%
Unvested Restricted Stock Units [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total		$ 18,700,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		2 years 73 days
Employee Stock Purchase Plan [Member]
Employee Stock Purchase Plan, Shares Reserved for Future Issuance		2,650,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	500,000
Percentage of Fair Value to Determine Price of Common Stock		85.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans		187,273	84,678	99,144
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		911,337
Equity Incentive Plan 2005 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	2,000,000
Percentage of Fair Value to Determine Price of Common Stock	100.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		2,503,918
Equity Incentive Plan 2005 [Member] | Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period			10 years
Equity Incentive Plan 2005 [Member] | Minimum [Member] | Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			1 year
Equity Incentive Plan 2005 [Member] | Maximum [Member] | Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			4 years
Postretirement Health Coverage [Member]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		$ 100,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		100,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		100,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		100,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		100,000
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		700,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total		$ 100,000	$ 100,000	$ 100,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		3.00%	4.10%	3.40%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year		7.40%
Defined Benefit Plan, Health Care Cost Trend Rate, Annual Rate of Change		0.40%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate		4.40%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate			2027
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components		$ 14,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components		12,000
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation		318,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation		270,000
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		100,000
Swiss Plan [Member]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax		(4,100,000)	$ (2,700,000)
Defined Benefit Plan, Expected Future Employee and Employer Contributions, Next Twelve Months		900,000
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		1,400,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		1,300,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		1,100,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		1,700,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		1,300,000
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		7,000,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total		$ 1,019,000	$ 1,008,000	$ 986,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		0.20%	0.90%
Swiss Plan [Member] | Debt Securities and Cash [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		62.00%
Swiss Plan [Member] | Real Estate Investments [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		17.00%
Swiss Plan [Member] | Alternative Investments [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		10.00%
Swiss Plan [Member] | Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		11.00%
Xcerra [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay		6.00%