Goodwill and Intangible Assets - Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Jan. 24, 2015	Jul. 26, 2014
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets Gross Excluding Goodwill	$ 201,235	$ 202,179
Finite-Lived Intangible Assets, Accumulated Amortization	87,062	86,063
Intangible assets, net	114,173	116,116
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	179,859	173,594
Finite-Lived Intangible Assets, Accumulated Amortization	75,979	69,048
Contract backlog
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	8,076	15,285
Finite-Lived Intangible Assets, Accumulated Amortization	6,874	13,490
Trade names
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	8,200	8,200
Finite-Lived Intangible Assets, Accumulated Amortization	4,005	3,361
Non-compete agreements
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	400	400
Finite-Lived Intangible Assets, Accumulated Amortization	204	164
UtiliQuest
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
UtiliQuest trade name	$ 4,700	$ 4,700