Customer Concentration and Revenue Information - Revenue Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 25, 2020	Jul. 27, 2019	Jul. 25, 2020	Jul. 27, 2019
Concentration Risk
Contract revenues	$ 823,921	$ 884,221	$ 1,638,244	$ 1,717,964
% of Total	100.00%	100.00%	100.00%	100.00%
Revenue Benchmark | Customer Concentration Risk
Concentration Risk
% of Total			10.00%
Revenue Benchmark | Customer Concentration Risk | Five Unnamed Customers
Concentration Risk
% of Total			77.50%	79.40%
Revenue Benchmark | Customer Concentration Risk | Verizon Communications Inc.
Concentration Risk
Contract revenues	$ 163,000	$ 205,000	$ 339,100	$ 384,800
% of Total	19.80%	23.20%	20.70%	22.40%
Revenue Benchmark | Customer Concentration Risk | CenturyLink, Inc.
Concentration Risk
Contract revenues	$ 158,400	$ 138,700	$ 307,100	$ 248,500
% of Total	19.20%	15.70%	18.70%	14.50%
Revenue Benchmark | Customer Concentration Risk | AT&T Inc.
Concentration Risk
Contract revenues	$ 134,600	$ 183,300	$ 288,600	$ 392,500
% of Total	16.30%	20.70%	17.60%	22.80%
Revenue Benchmark | Customer Concentration Risk | Comcast Corporation
Concentration Risk
Contract revenues	$ 131,400	$ 133,200	$ 249,300	$ 270,300
% of Total	15.90%	15.10%	15.20%	15.70%
Revenue Benchmark | Customer Concentration Risk | Total other customers combined
Concentration Risk
Contract revenues	$ 236,500	$ 224,000	$ 454,100	$ 421,900
% of Total	28.70%	25.30%	27.70%	24.60%