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Note 6 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Dec. 25, 2021 | Dec. 26, 2020 | 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 | $ 2,400 | $ 2,300 |
Deferred Compensation Liability, Current, Total | 1,100 | 1,600 |  |
Cash Surrender Value of Life Insurance | $ 1,400 | $ 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 | $ 200 | $ 8,400 | $ 1,300 |
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 | $ 21,600 |  |  |
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 | 0.00% |  |  |
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) | 160,855 | 161,351 | 242,633 |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares) | 346,498 |  |  |
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) | 914,705 |  |  |
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) | $ 382 | $ 241 |  |
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 | 4.90% | 2.50% | 2.10% |
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 | 6,800 | $ 900 |  |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) | 6,043 | 1,179 |  |
Defined Benefit Plan, Expected Future Employee and Employer Contributions, Next Twelve Months | 900 |  |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year One | 1,200 |  |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Two | 1,300 |  |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Three | 1,000 |  |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Four | 1,200 |  |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Five | 1,300 |  |  |
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years | 6,800 |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total | $ 395 | $ 1,228 | $ 1,469 |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate | 2.30% | 0.20% |  |
Swiss Plan [Member] | Debt Securities and Cash [Member] |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 54.00% |  |  |
Swiss Plan [Member] | Real Estate Investments [Member] |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 23.00% |  |  |
Swiss Plan [Member] | Alternative Investments [Member] |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 13.00% |  |  |
Swiss Plan [Member] | Defined Benefit Plan, Equity Securities [Member] |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 10.00% |  |  |
Pre Age 65 Plan [Member] | Postretirement Health Coverage [Member] |  |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year | 6.80% |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate, Annual Rate of Change | (0.27%) |  |  |
Post Age 65 Plan [Member] | Postretirement Health Coverage [Member] |  |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year | 7.20% |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate, Annual Rate of Change | (0.31%) |  |  |

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- Definition The annual rate of change increase (decrease) in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. + References No definition available. + Details
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- Definition Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(17)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Amount, after tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 + Details
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- Definition Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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- Definition Gross number of share options (or share units) granted during the period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(01) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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