Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 28, 2019	Dec. 29, 2018
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 720	$ 986
Expected return on plan assets	(320)	(431)
Amortization of net loss (gain)	862	866
Net periodic benefit cost	1,262	1,421
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	37	69
Amortization of prior service credits	(124)	(124)
Amortization of net loss (gain)	(197)	(190)
Net periodic benefit cost	$ (284)	$ (245)