Revenue - Disaggregation of Revenues by Service Type (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 29, 2026	Mar. 30, 2025
Disaggregation of Revenue [Line Items]
Revenue	$ 1,040.7	$ 1,164.9
Reporting Segments
Disaggregation of Revenue [Line Items]
Revenue	1,042.5	1,165.4
Reporting Segments \| Enterprise Talent Management
Disaggregation of Revenue [Line Items]
Revenue	459.2	529.1
Reporting Segments \| Science, Engineering & Technology
Disaggregation of Revenue [Line Items]
Revenue	289.2	327.3
Reporting Segments \| Education
Disaggregation of Revenue [Line Items]
Revenue	294.1	309.0
Reporting Segments \| Staffing Services
Disaggregation of Revenue [Line Items]
Revenue	691.3	793.5
Reporting Segments \| Staffing Services \| Enterprise Talent Management
Disaggregation of Revenue [Line Items]
Revenue	229.3	275.8
Reporting Segments \| Staffing Services \| Science, Engineering & Technology
Disaggregation of Revenue [Line Items]
Revenue	168.6	209.8
Reporting Segments \| Staffing Services \| Education
Disaggregation of Revenue [Line Items]
Revenue	293.4	307.9
Reporting Segments \| Outcome-based Services
Disaggregation of Revenue [Line Items]
Revenue	219.0	242.6
Reporting Segments \| Outcome-based Services \| Enterprise Talent Management
Disaggregation of Revenue [Line Items]
Revenue	106.8	133.2
Reporting Segments \| Outcome-based Services \| Science, Engineering & Technology
Disaggregation of Revenue [Line Items]
Revenue	112.2	109.4
Reporting Segments \| Outcome-based Services \| Education
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0
Reporting Segments \| Talent Solutions
Disaggregation of Revenue [Line Items]
Revenue	121.3	117.8
Reporting Segments \| Talent Solutions \| Enterprise Talent Management
Disaggregation of Revenue [Line Items]
Revenue	121.3	117.8
Reporting Segments \| Talent Solutions \| Science, Engineering & Technology
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0
Reporting Segments \| Talent Solutions \| Education
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0
Reporting Segments \| Permanent Placement
Disaggregation of Revenue [Line Items]
Revenue	10.9	11.5
Reporting Segments \| Permanent Placement \| Enterprise Talent Management
Disaggregation of Revenue [Line Items]
Revenue	1.8	2.3
Reporting Segments \| Permanent Placement \| Science, Engineering & Technology
Disaggregation of Revenue [Line Items]
Revenue	8.4	8.1
Reporting Segments \| Permanent Placement \| Education
Disaggregation of Revenue [Line Items]
Revenue	0.7	1.1
Intersegment
Disaggregation of Revenue [Line Items]
Revenue	$ (1.8)	$ (0.5)