Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 28, 2017	Jul. 29, 2017
Property, Plant and Equipment [Line Items]
Total	$ 951,069	$ 935,273
Less: accumulated depreciation	(527,739)	(513,166)
Property and equipment, net	423,330	422,107
Land
Property, Plant and Equipment [Line Items]
Total	3,470	3,470
Buildings
Property, Plant and Equipment [Line Items]
Total	$ 12,255	12,073
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	10 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	35 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	$ 13,985	13,912
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	1 year
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	10 years
Vehicles
Property, Plant and Equipment [Line Items]
Total	$ 505,327	496,820
Vehicles | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	1 year
Vehicles | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	5 years
Computer hardware and software
Property, Plant and Equipment [Line Items]
Total	$ 111,388	107,779
Computer hardware and software | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	1 year
Computer hardware and software | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	7 years
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Total	$ 13,190	12,226
Office furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	1 year
Office furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	10 years
Equipment and machinery
Property, Plant and Equipment [Line Items]
Total	$ 291,454	$ 288,993
Equipment and machinery | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	1 year
Equipment and machinery | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (Years)	10 years