Property and Equipment, net (Details) - USD ($) $ in Thousands	Jun. 27, 2020	Dec. 28, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 50,945	$ 45,333
Accumulated depreciation	(21,541)	(19,600)
Property and equipment, net	29,404	25,733
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,970	4,198
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,495	10,704
Survey and field equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	25,875	24,165
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,605	$ 6,266