Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 26, 2019	Jan. 27, 2018
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 327,267	$ 315,217
Accumulated Amortization	166,142	143,748
Intangible Assets, Net	161,125	171,469
UtiliQuest
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	4,700	4,700
Accumulated Amortization	0	0
Intangible Assets, Net	$ 4,700	4,700
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	11 years 1 month 6 days
Intangible Assets, Gross (Excluding Goodwill)	$ 312,017	299,717
Accumulated Amortization	157,691	135,544
Intangible Assets, Net	$ 154,326	164,173
Trade names
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	8 years
Intangible Assets, Gross (Excluding Goodwill)	$ 10,350	10,350
Accumulated Amortization	8,312	7,872
Intangible Assets, Net	$ 2,038	2,478
Non-compete agreements
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	1 year 6 months
Intangible Assets, Gross (Excluding Goodwill)	$ 200	450
Accumulated Amortization	139	332
Intangible Assets, Net	$ 61	$ 118