AOCI Related to Derivative Transactions (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)
Closed Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Estimated amount of derivatives to be reclassified in income from AOCI		(87)
Closed Contracts | Commodity price risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Estimated amount of derivatives to be reclassified in income from AOCI		(29)
Closed Contracts | Interest rate risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Estimated amount of derivatives to be reclassified in income from AOCI		(58)
Expiring in 2018
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		1,226
Expiring in 2018 | Commodity price risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		1,226
Expiring in 2019
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		1,505
Expiring in 2019 | Commodity price risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		1,505
Expiring in 2020
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		(69)
Expiring in 2020 | Commodity price risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		(69)
Closed or Expiring Over Next Three Years
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		2,575
Closed or Expiring Over Next Three Years | Commodity price risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		2,633
Closed or Expiring Over Next Three Years | Interest rate risk derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Net change in fair value of derivatives		$ (58)

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