Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 25, 2021	Dec. 26, 2020
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 559	$ 534
Expected return on plan assets	(354)	(319)
Amortization of net loss (gain)	599	898
Net periodic benefit cost	804	1,113
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	20	19
Amortization of prior service credits	(124)	(124)
Amortization of net loss (gain)	(181)	(181)
Net periodic benefit cost	$ (285)	$ (286)