Retirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands		4 Months Ended
		Jan. 17, 2021	Jan. 19, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension settlements			$ 38,600
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 4,532	5,076
Expected return on plan assets		(5,951)	(6,656)
Pension settlements		0	38,606
Actuarial loss (gain)	[1]	1,616	1,672
Amortization of unrecognized prior service cost	[1]	6	26
Net periodic benefit cost		203	38,724
Postretirement Healthcare Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost		173	248
Actuarial loss (gain)	[1]	(105)	6
Net periodic benefit cost		$ 68	$ 254

[1] Amounts were reclassified from accumulated OCI into net earnings as a component of “Other pension and post-retirement expenses, net