Acquisitions and Dispositions - Acquisitions Narrative (Details) - USD ($) $ in Millions				3 Months Ended		12 Months Ended
	Nov. 13, 2024	May 31, 2024	Mar. 07, 2022	Dec. 29, 2024	Jul. 03, 2022	Dec. 29, 2024	Dec. 31, 2023	Jan. 01, 2023
Business Acquisition [Line Items]
Goodwill, net				$ 304.2		$ 304.2	$ 151.1	$ 151.1
Goodwill impairment charge						72.8	$ 0.0	41.0
Children's Therapy Center (CTC) | Kelly Services USA, LLC (KSU)
Business Acquisition [Line Items]
Ownership percentage acquired (percent)	100.00%
Purchase price of acquisition	$ 3.3
Purchase price paid at closing	3.1
Goodwill, net	$ 3.0
Motion Recruitment Partners, LLC (MRP)
Business Acquisition [Line Items]
Ownership percentage acquired (percent)		100.00%
Purchase price of acquisition		$ 425.0
Purchase price paid at closing		440.0
Goodwill, net		222.9
Business combination, consideration transferred, other		3.4
Possible future contingent consideration		60.0
Contingent consideration, liability				0.0		0.0
Payments to acquire businesses, working capital adjustment				$ 1.4
Intangible assets acquired		145.9
Pro forma information, revenue of acquiree since acquisition date, actual						285.8
Pro forma information, earnings or loss of acquiree since acquisition date, actual						$ 4.2
Motion Recruitment Partners, LLC (MRP) | Customer relationships
Business Acquisition [Line Items]
Intangible assets acquired		$ 88.1
Acquired finite-lived intangible assets, weighted average useful life (years)		15 years
Motion Recruitment Partners, LLC (MRP) | Trade names
Business Acquisition [Line Items]
Intangible assets acquired		$ 56.5
Motion Recruitment Partners, LLC (MRP) | Trade names | Minimum
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life (years)		10 years
Motion Recruitment Partners, LLC (MRP) | Trade names | Maximum
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life (years)		15 years
Motion Recruitment Partners, LLC (MRP) | Non-compete agreements
Business Acquisition [Line Items]
Intangible assets acquired		$ 1.3
Acquired finite-lived intangible assets, weighted average useful life (years)		4 years
Pediatric Therapeutic Services
Business Acquisition [Line Items]
Ownership percentage acquired (percent)					100.00%
Purchase price of acquisition					$ 82.1
Purchase price paid at closing					$ 85.7
RocketPower
Business Acquisition [Line Items]
Ownership percentage acquired (percent)			100.00%
Purchase price of acquisition			$ 59.3
Purchase price paid at closing			$ 61.8
Goodwill impairment charge								$ 41.0