Effect of Derivative Instruments for Deferred Gains And (Losses) on Closed Contracts and Effective Portion in Fair Value on AOCI, Utilized for Risk Management Purposes (Detail) - USD ($) $ in Thousands		4 Months Ended
		Apr. 18, 2020	Apr. 20, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in AOCI on Derivatives(Effective Portion)	[1]	$ (3,849)	$ (9,593)
Production costs		670,873	652,141
Income before income taxes		(7,791)	86,065
Reclassification out of Accumulated Other Comprehensive Income
Derivative Instruments, Gain (Loss) [Line Items]
Income before income taxes	[2]	(411)	2,178
Interest Rate Contracts | Reclassification out of Accumulated Other Comprehensive Income
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	[2]	(33)	(33)
Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in AOCI on Derivatives(Effective Portion)	[1]	(3,849)	(9,593)
Commodity Contract | Reclassification out of Accumulated Other Comprehensive Income | Product
Derivative Instruments, Gain (Loss) [Line Items]
Production costs	[2],[3]	$ (378)	$ 2,211

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

[2] Amounts in parentheses, if any, indicate credits to determine net income.

[3] Included in materials, supplies, labor and other production costs (exclusive of depreciation and amortization shown separately).