Customer Concentration and Revenue Information - Revenue Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 24, 2020	Oct. 26, 2019	Oct. 24, 2020	Oct. 26, 2019
Concentration Risk
Contract revenues	$ 810,256	$ 884,115	$ 2,448,500	$ 2,602,079
% 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			75.60%	78.70%
Revenue Benchmark | Customer Concentration Risk | Verizon Communications Inc.
Concentration Risk
Contract revenues	$ 144,800	$ 182,100	$ 483,800	$ 566,900
% of Total	17.90%	20.60%	19.80%	21.80%
Revenue Benchmark | Customer Concentration Risk | Lumen Technologies(1)
Concentration Risk
Contract revenues	$ 134,400	$ 164,100	$ 441,500	$ 412,700
% of Total	16.60%	18.60%	18.00%	15.90%
Revenue Benchmark | Customer Concentration Risk | AT&T Inc.
Concentration Risk
Contract revenues	$ 118,900	$ 162,900	$ 407,500	$ 555,400
% of Total	14.70%	18.40%	16.60%	21.30%
Revenue Benchmark | Customer Concentration Risk | Comcast Corporation
Concentration Risk
Contract revenues	$ 143,600	$ 131,300	$ 393,000	$ 401,600
% of Total	17.70%	14.90%	16.00%	15.40%
Revenue Benchmark | Customer Concentration Risk | Total other customers combined
Concentration Risk
Contract revenues	$ 268,600	$ 243,700	$ 722,700	$ 665,500
% of Total	33.10%	27.60%	29.50%	25.60%