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Retirement Plans (Fair Values of Qualified Plan's Assets) (Details) - USD ($) $ in Thousands | Sep. 27, 2020 | Sep. 29, 2019
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 365,510 | $ 476,194
Cash and cash equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 3,665 | 10,110
Domestic equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 83,676 | 99,124
International equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 81,228 | 94,953
Investment grade |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 126,630 | 177,500
High yield |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 9,270 | 9,256
Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 29,375 | 42,052
Real estate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 31,666 | 43,199
Quoted Prices in Active Markets for Identical (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 136,271 | 155,642
Quoted Prices in Active Markets for Identical (Level 1) | Cash and cash equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Quoted Prices in Active Markets for Identical (Level 1) | Domestic equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 83,676 | 99,124
Quoted Prices in Active Markets for Identical (Level 1) | International equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 40,319 | 47,262
Quoted Prices in Active Markets for Identical (Level 1) | Investment grade |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 3,006 | 0
Quoted Prices in Active Markets for Identical (Level 1) | High yield |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 9,270 | 9,256
Quoted Prices in Active Markets for Identical (Level 1) | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Quoted Prices in Active Markets for Identical (Level 1) | Real estate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 127,289 | 187,610
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 3,665 | 10,110
Significant Other Observable Inputs (Level 2) | Domestic equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Other Observable Inputs (Level 2) | International equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Other Observable Inputs (Level 2) | Investment grade |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 123,624 | 177,500
Significant Other Observable Inputs (Level 2) | High yield |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Other Observable Inputs (Level 2) | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Other Observable Inputs (Level 2) | Real estate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | Domestic equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | International equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | Investment grade |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | High yield |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Significant Unobservable Inputs (Level 3) | Real estate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 0 | $ 0

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