Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 987	$ 943	$ 2,958	$ 2,833
Expected return on plan assets	(432)	(473)	(1,293)	(1,420)
Amortization of net loss (gain)	867	920	2,600	2,762
Net periodic benefit cost	1,422	1,390	4,265	4,175
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	69	69	206	208
Amortization of prior service credits	(125)	(124)	(374)	(374)
Amortization of net loss (gain)	(190)	(163)	(570)	(491)
Net periodic benefit cost	$ (246)	$ (218)	$ (738)	$ (657)