Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 30, 2016	Jul. 25, 2015
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets Gross Excluding Goodwill	$ 309,920	$ 216,986
Accumulated amortization:	112,041	96,060
Intangible assets, net	197,879	120,926
Finite-Lived Intangible Assets, Period Increase (Decrease)	$ 3,400
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	12 years 8 months 12 days
Carrying amount	$ 289,955	195,375
Accumulated amortization:	$ 101,012	83,772
Contract backlog
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	3 months 18 days
Carrying amount	$ 4,780	8,076
Accumulated amortization:	$ 4,666	7,381
Trade names
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	7 years 1 month 6 days
Carrying amount	$ 9,800	8,200
Accumulated amortization:	$ 6,034	4,650
Non-compete agreements
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	2 years 7 months 6 days
Carrying amount	$ 685	635
Accumulated amortization:	329	257
UtiliQuest
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
UtiliQuest trade name	$ 4,700	$ 4,700