Note 6 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 25, 2021	Dec. 26, 2020	Dec. 26, 2020	Dec. 28, 2019	May 08, 2019
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	$ 2,400		$ 2,300	$ 2,000
Deferred Compensation Liability, Current, Total	1,600	$ 1,800	1,800
Cash Surrender Value of Life Insurance	$ 1,800	$ 1,800	1,800
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	0	0		0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 8,400		$ 1,300	$ 200
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 400
Restricted Stock Units (RSUs) [Member] | Vesting Over One Year Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	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 (Year)	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 (Year)	4 years
Equity Based Performance Stock Units Granted in 2020, 2019, 2018, and 2017 [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	$ 19,500
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years 3 months 18 days
Minimum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Shares Available for Issue	25.00%
Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Shares Available for Issue	200.00%
Employee Stock Purchase Plan [Member]
Employee Stock Purchase Plan, Shares Reserved for Future Issuance (in shares)	2,650,000
Percentage of Fair Value to Determine Price of Common Stock	85.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)	161,351		242,633	187,273
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)	507,353
Equity Incentive Plan 2005 [Member]
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 (in shares)	1,375,536
Equity Incentive Plan 2005 [Member] | Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	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 (Year)	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 (Year)	4 years
Postretirement Health Coverage [Member]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ 241		$ 134
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	100
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	100
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	100
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	100
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years	$ 600
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total			$ 100	$ 100
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.50%	2.10%	2.10%	3.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	6.60%
Defined Benefit Plan, Health Care Cost Trend Rate, Annual Rate of Change	0.28%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	4.40%
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 100
Swiss Plan [Member]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	900	$ (1,300)	$ (1,300)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	1,179		1,916
Defined Benefit Plan, Expected Future Employee and Employer Contributions, Next Twelve Months	900
Defined Benefit Plan, Expected Future Benefit Payment, Year One	900
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	1,500
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	1,300
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	1,100
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	1,200
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years	6,400
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ 1,228		$ 1,469	$ 1,019
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	0.20%	0.20%	0.20%
Swiss Plan [Member] | Debt Securities and Cash [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	57.00%
Swiss Plan [Member] | Real Estate Investments [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	21.00%
Swiss Plan [Member] | Alternative Investments [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	12.00%
Swiss Plan [Member] | Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%