Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) (USD $)	3 Months Ended		6 Months Ended
	Jan. 25, 2014	Jan. 26, 2013	Jan. 25, 2014	Jan. 26, 2013	Jul. 27, 2013	Dec. 03, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 4,800,000	$ 5,000,000	$ 9,900,000	$ 6,500,000
Carrying amount						90,600,000
Gross Intangible Assets	192,979,000		192,979,000		193,082,000
Net Intangible Assets	115,243,000		115,243,000		125,275,000
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Carrying amount	164,394,000		164,394,000		164,497,000
Accumulated Amortization	62,620,000		62,620,000		56,219,000
Contract Backlog
Finite-Lived Intangible Assets [Line Items]
Carrying amount	15,285,000		15,285,000		15,285,000
Accumulated Amortization	12,276,000		12,276,000		9,433,000
Trade Names
Finite-Lived Intangible Assets [Line Items]
Carrying amount	8,200,000		8,200,000		8,200,000
Accumulated Amortization	2,716,000		2,716,000		2,071,000
UtiliQuest trade name
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining, Useful Lives			0 years
Indefinite-Lived Intangible Assets	4,700,000		4,700,000		4,700,000
Noncompete Agreements
Finite-Lived Intangible Assets [Line Items]
Carrying amount	400,000		400,000		400,000
Accumulated Amortization	$ 124,000		$ 124,000		$ 84,000