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