Concentration of Credit Risk - Customer Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 28, 2018	Apr. 29, 2017
Concentration Risk
Contract revenues	$ 731,375	$ 786,338
Concentration risk percentage	100.00%	100.00%
Customer Concentration Risk | Sales Revenue, Services, Net
Concentration Risk
Concentration risk percentage	10.00%
Customer Concentration Risk | Sales Revenue, Services, Net | Telecommunications
Concentration Risk
Contract revenues	$ 667,200	$ 725,300
Concentration risk percentage	91.20%	92.20%
Customer Concentration Risk | Sales Revenue, Services, Net | Underground facility locating
Concentration Risk
Contract revenues	$ 45,100	$ 42,100
Concentration risk percentage	6.20%	5.40%
Customer Concentration Risk | Sales Revenue, Services, Net | Electrical and gas utilities and other
Concentration Risk
Contract revenues	$ 19,100	$ 18,900
Concentration risk percentage	2.60%	2.40%