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Retirement Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 30, 2018
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2,499	$ 3,080	$ 2,894
Actuarial loss	1,652	1,207	1,538
Service cost	0	0	490
Amortization of unrecognized prior service cost	85	115	146
Net periodic benefit (credit) cost	4,236	4,402	5,068
Postretirement Health Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost	807	997	955
Actuarial loss	18	(159)	(27)
Service cost	0	0
Net periodic benefit (credit) cost	825	838	928
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	13,377	19,825	19,463
Expected return on plan assets	(19,578)	(26,334)	(26,467)
Pension settlements	39,218	0	0
Actuarial loss	3,644	2,754	3,331
Service cost	0	0
Net periodic benefit (credit) cost	$ 36,661	$ (3,755)	$ (3,673)

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Defined Benefit Plan, Pension Settlements

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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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