Accounts Receivable Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 26, 2019	Oct. 27, 2018	Oct. 26, 2019	Oct. 27, 2018	Jan. 26, 2019
Concentration Risk
Accounts receivable, net	$ 919,496		$ 919,496		$ 625,258
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Verizon Communications Inc.
Concentration Risk
Accounts receivable, net	$ 160,200		$ 160,200		$ 127,200
Concentration risk percentage			12.90%		15.40%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | AT&T Inc.
Concentration Risk
Accounts receivable, net	511,300		$ 511,300		$ 298,400
Concentration risk percentage			41.10%		36.20%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Comcast Corporation
Concentration Risk
Accounts receivable, net	200,900		$ 200,900		$ 147,200
Concentration risk percentage			16.10%		17.90%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | AT&T Inc.
Concentration Risk
Accounts receivable, net	$ 111,300		$ 111,300		$ 90,600
Concentration risk percentage			8.90%		11.00%