Accounts Receivable Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Apr. 27, 2019	Apr. 28, 2018	Jan. 26, 2019
Concentration Risk
Accounts receivable, net	$ 701,522		$ 625,258
Concentration risk percentage	100.00%	100.00%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | AT&T Inc.
Concentration Risk
Accounts receivable, net	$ 131,100		$ 127,200
Concentration risk percentage	13.30%		15.40%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Comcast Corporation
Concentration Risk
Accounts receivable, net	$ 390,300		$ 298,400
Concentration risk percentage	39.60%		36.20%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Comcast Corporation
Concentration Risk
Accounts receivable, net	$ 152,700		$ 147,200
Concentration risk percentage	15.50%		17.90%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | AT&T Inc.
Concentration Risk
Accounts receivable, net	$ 114,300		$ 90,600
Concentration risk percentage	11.60%		11.00%