SUPPLEMENTAL BALANCE SHEET INFORMATION - Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2025	Dec. 29, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 284,882	$ 282,355
Less accumulated depreciation	(206,401)	(192,753)
Less impairment charge	(5,364)	0
Property and equipment, net	73,117	89,602
Capitalized computer software, net	67,200	76,300
Depreciation expense	26,300	25,500	$ 20,600
Depreciation expense included in cost of services	4,000	900
Buildings and land
Property, Plant and Equipment [Line Items]
Gross property and equipment	23,550	23,537
Software
Property, Plant and Equipment [Line Items]
Gross property and equipment	226,573	220,095
Construction in progress
Property, Plant and Equipment [Line Items]
Gross property and equipment	1,014	838
Computers, furniture and equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 33,745	$ 37,885