Pension and Other Postretirement Benefit Plans - Schedule of Pension Plans' Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019
Component:
Service cost	$ 1,464	$ 1,212	$ 4,394	$ 5,545
Interest cost	13,030	17,088	39,092	52,916
Expected return on plan assets	(27,666)	(26,291)	(82,996)	(79,709)
Amortization of previously unrecognized items	3,109	3,182	9,329	9,353
Plan Amendment and settlement loss (gain)	0	0	2,651	(34,621)
Net periodic benefit cost	$ (10,063)	$ (4,809)	$ (27,530)	$ (46,516)