Accounts Receivable, Contract Assets, and Contract Liabilities - Customer Credit Concentration (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Oct. 24, 2020	Apr. 25, 2020	Oct. 26, 2019	Oct. 24, 2020	Oct. 26, 2019	Jan. 25, 2020
Concentration Risk
Amount	$ 938,941			$ 938,941		$ 817,245
% of Total	100.00%		100.00%	100.00%	100.00%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Verizon Communications Inc.
Concentration Risk
Amount	$ 415,600			$ 415,600		440,200
% of Total		41.80%		36.90%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Lumen Technologies(1)
Concentration Risk
Amount	198,900			$ 198,900		175,800
% of Total		16.70%		17.60%
Customer Concentration Risk | Trade Accounts Receivable and Costs and Estimated Earnings | Comcast Corporation
Concentration Risk
Amount	$ 156,200			$ 156,200		$ 114,000
% of Total		10.80%		13.90%