Accounts Receivable Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 25, 2020	Apr. 27, 2019	Jul. 27, 2019	Jan. 25, 2020
Concentration Risk
Accounts receivable, net (Note 5)	$ 870,791			$ 817,245
Concentration risk percentage	100.00%	100.00%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Verizon Communications Inc.
Concentration Risk
Accounts receivable, net (Note 5)	$ 471,200			440,200
Concentration risk percentage	41.90%		41.80%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | CenturyLink, Inc.
Concentration Risk
Accounts receivable, net (Note 5)	$ 204,600			175,800
Concentration risk percentage	18.20%		16.70%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Comcast Corporation
Concentration Risk
Accounts receivable, net (Note 5)	$ 130,000			$ 114,000
Concentration risk percentage	11.60%		10.80%