Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		4 Months Ended
		Apr. 24, 2021	Apr. 18, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)		$ 71,655	$ (5,772)
Pension and postretirement plans:
Settlement and curtailment loss			86,865
Net loss for the period			15,693
Amortization of prior service cost included in net income		13	55
Amortization of actuarial loss included in net income		123	953
Pension and postretirement plans, net of tax		136	103,566
Derivative instruments:
Net change in fair value of derivatives	[1]	4,745	(3,849)
Loss reclassified to net income		220	411
Derivative instruments, net of tax		4,965	(3,438)
Other comprehensive income, net of tax		5,101	100,128
Comprehensive income		$ 76,756	$ 94,356

[1] Amounts in parentheses indicate debits to determine net income.