Property and Equipment (Details) (USD $)	3 Months Ended
	Oct. 27, 2012	Oct. 29, 2011	Jul. 28, 2012
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 438,988,000		$ 435,872,000
Less: accumulated depreciation	(284,287,000)		(277,625,000)
Property and equipment, net	154,701,000		158,247,000
Depreciation and repairs and maintenance expenses [Abstract]
Depreciation expense	13,720	14,268
Repairs and maintenance expense	3,811	4,532
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,915,000		2,915,000
Buildings
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	10,630,000		10,630,000
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,668,000		4,674,000
Vehicles
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	221,083,000		220,669,000
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	59,694,000		57,965,000
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	5,649,000		5,552,000
Equipment and machinery
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 134,349,000		$ 133,467,000
Maximum | Buildings
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	35 years
Maximum | Leasehold Improvements
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Maximum | Vehicles
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Maximum | Office furniture and equipment
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum | Equipment and machinery
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Minimum | Buildings
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Minimum | Leasehold Improvements
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum | Vehicles
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum | Office furniture and equipment
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum | Equipment and machinery
Property, Plant and Equipment [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years