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Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands | Jan. 27, 2018 | Jul. 29, 2017 | Jul. 30, 2016
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Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 315,217 | $ 315,217 | $ 309,920
Accumulated Amortization | 143,748 | 131,656 | 112,041
Intangible Assets, Net | 171,469 | 183,561 | 197,879
UtiliQuest |  |  |
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 4,700 | 4,700 | 4,700
Accumulated Amortization | 0 | 0 | 0
Intangible Assets, Net | 4,700 | 4,700 | 4,700
Customer relationships |  |  |
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 299,717 | 299,717 | 289,955
Accumulated Amortization | 135,544 | 124,084 | 101,012
Intangible Assets, Net | 164,173 | 175,633 | 188,943
Trade names |  |  |
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 10,350 | 10,350 | 9,800
Accumulated Amortization | 7,872 | 7,285 | 6,034
Intangible Assets, Net | 2,478 | 3,065 | 3,766
Non-compete agreements |  |  |
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 450 | 450 | 685
Accumulated Amortization | 332 | 287 | 329
Intangible Assets, Net | $ 118 | $ 163 | 356
Contract backlog |  |  |
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible Assets, Gross (Excluding Goodwill) |  |  | 4,780
Accumulated Amortization |  |  | 4,666
Intangible Assets, Net |  |  | $ 114

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- Definition Finite-Lived and Indefinite-Lived Intangible Assets + References No definition available. + Details
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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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