Credit Facility - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended
	Apr. 29, 2011	Jan. 31, 2015	Jan. 25, 2014
Line of Credit Facility [Line Items]
Line of credit facility, amount outstanding		0	$ 0
Letters of credit, outstanding amount		67,264,000	34,363,000
Amended Credit Agreement
Line of Credit Facility [Line Items]
Credit facility, borrowing capacity	1,000,000,000
Credit facility maturity term, in years	5 years
Option to increase in commitments under credit agreement, maximum	300,000,000
Credit facility, expiration date		Apr. 29, 2016
Percentage of Loan Cap under Amended Credit Agreement	10.00%
Amount of Loan Cap under Amended Credit Agreement	$ 50,000,000