Goodwill and 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 and Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 267,810,000		$ 267,810,000		$ 267,810,000	$ 87,900,000
Amortization expense for finite-lived intangible assets	4,800,000	5,000,000	9,900,000	6,500,000
UtiliQuest trade name
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Goodwill					35,600,000
Indefinite-Lived Intangible Assets	$ 4,700,000		$ 4,700,000		$ 4,700,000
Margin of excess					20.00%
Goodwill [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Fair Value Inputs, Discount Rate			11.50%
Maximum | Goodwill [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Fair Value Assumptions, Terminal Growth Rate			2.00%