Customer Concentration and Revenue Information - Revenue Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 25, 2020	Jul. 31, 2021	Jul. 25, 2020
Concentration Risk
Contract revenues	$ 787,568	$ 823,921	$ 1,515,065	$ 1,638,244
% of Total	100.00%	100.00%	100.00%	100.00%
Revenue Benchmark | Customer Concentration Risk | AT&T Inc.
Concentration Risk
Contract revenues	$ 177,500	$ 134,600	$ 333,100	$ 288,600
% of Total	22.50%	16.30%	22.00%	17.60%
Revenue Benchmark | Customer Concentration Risk | Comcast Corporation
Concentration Risk
Contract revenues	$ 121,700	$ 131,400	$ 252,800	$ 249,300
% of Total	15.50%	15.90%	16.70%	15.20%
Revenue Benchmark | Customer Concentration Risk | Verizon Communications Inc.
Concentration Risk
Contract revenues	$ 90,800	$ 163,000	$ 182,300	$ 339,100
% of Total	11.50%	19.80%	12.00%	20.70%
Revenue Benchmark | Customer Concentration Risk | Lumen Technologies
Concentration Risk
Contract revenues	$ 95,400	$ 158,400	$ 181,200	$ 307,100
% of Total	12.10%	19.20%	12.00%	18.70%
Revenue Benchmark | Customer Concentration Risk | Total other customers combined
Concentration Risk
Contract revenues	$ 302,200	$ 236,500	$ 565,700	$ 454,100
% of Total	38.40%	28.70%	37.30%	27.70%