Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Mar. 28, 2020	Mar. 30, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 720	$ 985	$ 1,440	$ 1,971
Expected return on plan assets	(320)	(430)	(640)	(861)
Amortization of net loss (gain)	862	867	1,724	1,733
Net periodic benefit cost	1,262	1,422	2,524	2,843
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	38	68	75	137
Amortization of prior service credits	(125)	(125)	(249)	(249)
Amortization of net loss (gain)	(196)	(190)	(393)	(380)
Net periodic benefit cost	$ (283)	$ (247)	$ (567)	$ (492)