Customer Concentration and Revenue Information - Narratives (Details) $ in Thousands	3 Months Ended								6 Months Ended		12 Months Ended
	Jan. 25, 2020 USD ($)	Oct. 26, 2019 USD ($)	Jul. 27, 2019 USD ($)	Apr. 27, 2019 USD ($)	Jan. 26, 2019 USD ($) customer	Oct. 27, 2018 USD ($)	Jul. 28, 2018 USD ($)	Apr. 28, 2018 USD ($)	Jan. 27, 2018 USD ($)	Jan. 28, 2017 USD ($)	Jan. 25, 2020 USD ($)	Jan. 26, 2019 USD ($) customer	Jul. 29, 2017 USD ($)
Concentration Risk [Line Items]
Number of customers classified as highly concentrated | customer					5							5
Concentration risk percentage									100.00%		100.00%	100.00%	100.00%
Revenues	$ 737,603	$ 884,115	$ 884,221	$ 833,743	$ 748,619	$ 848,237	$ 799,470	$ 731,375	$ 1,411,348	$ 1,500,355	$ 3,339,682	$ 3,127,700	$ 3,066,880
Sales Revenue, Services, Net | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage											10.00%
Sales Revenue, Services, Net | Customer Concentration Risk | Five Unnamed Customers
Concentration Risk [Line Items]
Concentration risk percentage									75.80%		78.40%	78.40%	76.80%
Sales Revenue, Services, Net | Customer Concentration Risk | Windstream
Concentration Risk [Line Items]
Revenues												$ 113,600