Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 985	$ 944	$ 1,971	$ 1,888
Expected return on plan assets	(430)	(473)	(861)	(947)
Amortization of net loss (gain)	867	921	1,733	1,842
Net periodic benefit cost	1,422	1,392	2,843	2,783
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	68	70	137	139
Amortization of prior service credits	(125)	(124)	(249)	(248)
Amortization of net loss (gain)	(190)	(164)	(380)	(328)
Net periodic benefit cost	$ (247)	$ (218)	$ (492)	$ (437)