Goodwill and Intangible Assets - Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Oct. 25, 2014	Jul. 26, 2014
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets Gross Excluding Goodwill	$ 206,237	$ 202,179
Accumulated amortization	88,413	86,063
Net Intangible Assets	117,824	116,116
Customer Relationships
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	179,391	173,594
Accumulated amortization	72,483	69,048
Backlog
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	13,546	15,285
Accumulated amortization	12,063	13,490
Trade Names
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	8,200	8,200
Accumulated amortization	3,683	3,361
Noncompete Agreements
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	400	400
Accumulated amortization	184	164
UtiliQuest
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 4,700	$ 4,700