Retirement Plans (Fair Value of Plan Assets of Pension Plans) (Details) - USD ($) $ in Thousands	Sep. 27, 2020	Sep. 29, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 365,510	$ 476,194
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	78,971	79,893	$ 73,067
Accumulated benefit obligation	78,971	79,893
Fair value of plan assets	0	0	0
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	412,573	521,931	457,109
Accumulated benefit obligation	412,573	521,931
Fair value of plan assets	$ 365,510	$ 476,194	$ 456,127