Business and basis of presentation - Details of Company Operated Stores in Following States (Detail)

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Business and basis of presentation - Details of Company Operated Stores in Following States (Detail)	Oct. 27, 2012 Store
Business And Basis Of Presentation [Line Items]
Number of stores	537
Montana [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
Nebraska [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	3
Nevada [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	6
New Hampshire [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
New Jersey [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	14
New Mexico [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
New York [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	18
North Carolina [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	17
North Dakota [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
Ohio [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	18
Oklahoma [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	8
Oregon [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	6
Pennsylvania [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	20
Rhode Island [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
South Carolina [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	10
Tennessee [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	8
Texas [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	65
Utah [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	6
Virginia [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	12
Washington [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	9
West Virginia [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
Wisconsin [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	7
Alabama [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	10
Arizona [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	23
Arkansas [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	4
California [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	53
Colorado [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	12
Connecticut [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	4
Delaware [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	1
Florida [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	38
Georgia [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	21
Idaho [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	3
Illinois [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	38
Indiana [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	10
Iowa [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	6
Kansas [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	3
Kentucky [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	6
Louisiana [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	8
Maine [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	2
Maryland [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	9
Massachusetts [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	7
Michigan [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	23
Minnesota [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	11
Mississippi [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	4
Missouri [Member]
Business And Basis Of Presentation [Line Items]
Number of stores	8