Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 29, 2017	Apr. 23, 2016	Apr. 29, 2017	Apr. 23, 2016	Jul. 30, 2016
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 315,452		$ 315,452		$ 309,920
Accumulated Amortization	125,601		125,601		112,041
Intangible Assets, Net	189,851		189,851		197,879
Amortization of intangible assets	6,200	$ 4,500	18,500	$ 14,000
UtiliQuest
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	4,700		4,700		4,700
Intangible Assets, Net	$ 4,700		4,700		4,700
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	12 years 4 months
Intangible Assets, Gross (Excluding Goodwill)	$ 299,717		299,717		289,955
Accumulated Amortization	118,203		118,203		101,012
Intangible Assets, Net	$ 181,514		181,514		188,943
Trade names
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	7 years 4 months
Intangible Assets, Gross (Excluding Goodwill)	$ 10,350		10,350		9,800
Accumulated Amortization	6,914		6,914		6,034
Intangible Assets, Net	$ 3,436		3,436		3,766
Non-compete agreements
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	2 years 6 months
Intangible Assets, Gross (Excluding Goodwill)	$ 685		685		685
Accumulated Amortization	484		484		329
Intangible Assets, Net	$ 201		201		356
Contract backlog
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Weighted average remaining useful lives (in years)	0 years
Intangible Assets, Gross (Excluding Goodwill)	$ 0		0		4,780
Accumulated Amortization	0		0		4,666
Intangible Assets, Net	0		$ 0		$ 114
Decrease in intangible assets	$ 4,800