Accumulated Other Comprehensive Income (Loss) Related to Derivative Transactions (Detail) (USD $)	4 Months Ended
	Apr. 20, 2013	Apr. 21, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	$ (8,621,000)	$ (7,009,000)
Closed Or Expiring Over The Next Four Years
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	11,700,000
Closed Or Expiring Over The Next Four Years | Closed Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Estimated amount of derivatives to be reclassified in income from AOCI	7,200,000
Closed Or Expiring Over The Next Four Years | Expiring in 2013
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	4,400,000
Closed Or Expiring Over The Next Four Years | Expiring in 2016
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	100,000
Commodity price risk derivatives | Closed Or Expiring Over The Next Four Years
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	10,200,000
Commodity price risk derivatives | Closed Or Expiring Over The Next Four Years | Closed Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Estimated amount of derivatives to be reclassified in income from AOCI	5,900,000
Commodity price risk derivatives | Closed Or Expiring Over The Next Four Years | Expiring in 2013
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	4,200,000
Commodity price risk derivatives | Closed Or Expiring Over The Next Four Years | Expiring in 2016
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	100,000
Interest rate risk derivatives | Closed Or Expiring Over The Next Four Years
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	1,500,000
Interest rate risk derivatives | Closed Or Expiring Over The Next Four Years | Closed Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Estimated amount of derivatives to be reclassified in income from AOCI	1,300,000
Interest rate risk derivatives | Closed Or Expiring Over The Next Four Years | Expiring in 2013
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss) related to commodity price risk and interest rate risk derivative transactions	$ 200,000