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. 21, 2018	Apr. 22, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives	[1]	$ 10,470	$ (3,518)
Production costs		625,122	608,068
Income before income taxes		69,781	95,077
Reclassification out of Accumulated Other Comprehensive Income
Derivative Instruments, Gain (Loss) [Line Items]
Income before income taxes	[2]	297	474
Interest Rate Contracts | Reclassification out of Accumulated Other Comprehensive Income
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	[2]	33	27
Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives	[1]	10,470	(3,518)
Commodity Contract | Reclassification out of Accumulated Other Comprehensive Income
Derivative Instruments, Gain (Loss) [Line Items]
Production costs	[2],[3]	$ 264	$ 447

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

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

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