Customer Concentration and Revenue Information - Customer Type (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%
Customer Concentration Risk | Revenue Benchmark
Concentration Risk
% of Total			10.00%
Customer Concentration Risk | Revenue Benchmark | Telecommunications
Concentration Risk
Contract revenues	$ 721,200	$ 798,100	$ 2,193,900	$ 2,363,900
% of Total	89.00%	90.30%	89.60%	90.80%
Customer Concentration Risk | Revenue Benchmark | Underground facility locating
Concentration Risk
Contract revenues	$ 59,000	$ 56,000	$ 171,300	$ 158,000
% of Total	7.30%	6.30%	7.00%	6.10%
Customer Concentration Risk | Revenue Benchmark | Electrical and gas utilities and other
Concentration Risk
Contract revenues	$ 30,100	$ 30,000	$ 83,300	$ 80,200
% of Total	3.70%	3.40%	3.40%	3.10%
Five Unnamed Customers | Customer Concentration Risk | Revenue Benchmark
Concentration Risk
% of Total			75.60%	78.70%