Goodwill and Intangible Assets - Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Apr. 25, 2015	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	91,204		86,063
Intangible assets, net	110,031		116,116
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	179,859	400	173,594
Finite-Lived Intangible Assets, Accumulated Amortization	79,531		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	7,121		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	4,328		3,361
Non-compete agreements
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Carrying amount	400		400
Finite-Lived Intangible Assets, Accumulated Amortization	224		164
UtiliQuest
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
UtiliQuest trade name	$ 4,700		$ 4,700