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Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 26, 2020 | Dec. 28, 2019 | Dec. 29, 2018
Significant Accounting Policies [Line Items] |  |  |
Fiscal Period Duration | 364 days | 364 days | 364 days
Unrealized gain (loss) on equity securities | $ (1,791) | $ 1,975 | $ (1,606)
Accounts Receivable, Allowance for Credit Loss | $ 2,400 | 2,800 |
Percentage of facilities under operating lease | 51.00% |  |
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months | $ 444 |  |
Finite-Lived Intangible Assets, Amortization Expense, Year Two | 320 |  |
Finite-Lived Intangible Assets, Amortization Expense, Year Three | 310 |  |
Finite-Lived Intangible Assets, Amortization Expense, Year Four | 310 |  |
Finite-Lived Intangible Assets, Amortization Expense, Year Five | 147 |  |
Impairment of Long-Lived Assets Held-for-use | 0 | 0 | 1,532
Self Insurance, Annual Maximum of Health Claims Liability per Associate | 500 |  |
Stop loss insurance aggregating deductible | 450 |  |
Cost of Goods Sold, Vendor Allowances | 133,500 | 130,400 | 132,000
Vendor Paid Cooperative Advertising Credits | 21,700 | 24,800 | 19,400
Accounts Receivable, Earned Advertising Credits | 886,000 | 1,000 |
Accounts Receivable, Earned Promotional Discounts | 8,600 | 9,500 |
Unearned Income for Vendor Programs | 3,300 | 5,400 |
Advertising Expense | 24,500 | 30,300 | 30,500
Commission income | 17,700 | 18,300 | $ 17,900
Investments [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Cash Equivalents, at Carrying Value | 95,900 | 32,900 |
Consumer Electronic Payments [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Cash Equivalents, at Carrying Value | $ 41,700 | $ 23,100 |
Maximum [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Lease renewal term | 20 years |  |
Self Insurance, Maximum of Workers Compensation Claims Liability per Associate per Claim | $ 2,000 |  |
Property and Casualty Insurance, Deductible | $ 1,000 |  |
Minimum [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Lease renewal term | 5 years |  |
Self Insurance, Maximum of Workers Compensation Claims Liability per Associate per Claim | $ 1,000 |  |
Property and Casualty Insurance, Deductible | $ 100 |  |
Customer Lists [Member] | Maximum [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life | 10 years |  |

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- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -SubTopic 35 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848 + Details
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- Definition Percentage of open store facilities leased through operating leasing arrangements. + References No definition available. + Details
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- Definition Primarily represents commissions incurred in the period based upon the sale by commissioned employees or third parties of the entity's goods or services, and fees for sales assistance or product enhancements performed by third parties (such as a distributor or value added reseller), net of commission income. + References No definition available. + Details
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- Definition Self Insurance, Annual Maximum of Health Claims Liability per Associate + References No definition available. + Details
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- Definition Stop loss insurance aggregating deductible. + References No definition available. + Details
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