Acquisitions and Dispositions - Additional Information (Details) - USD ($) $ in Millions						1 Months Ended	9 Months Ended	12 Months Ended
		Sep. 29, 2023	Jan. 17, 2022	Dec. 31, 2021	Oct. 01, 2021	Nov. 30, 2021	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Net								$ 339.2	$ 371.9
Income tax adjustments							$ 3.1
Total cash consideration paid for acquisitions, net of cash acquired								0.0	20.2	$ 8.1
Payment for contingent consideration liability, financing activities									3.8	6.3
Goodwill acquired during the period	[1]								2.3
Cash proceeds for segment consideration		$ 6.5	$ 3.2
Net loss on disposition			8.0				4.1		2.1
Carrying value, intangible assets								339.2	371.9
Revenues from services	[2]							18,914.5	19,827.5	20,724.4
Acquisitions and integration costs								$ 53.3
Interest and Other Expenses (Income), Net
Business Acquisition [Line Items]
Net loss on disposition			1.7						1.2
Selling and Administrative Expenses
Business Acquisition [Line Items]
Net loss on disposition		$ 1.3	$ 9.7			$ 1.2			0.9
2021 Acquisitions Excluding Ettain Group [Member]
Business Acquisition [Line Items]
Goodwill acquired during the period									8.8
Intangible assets acquired during the period									$ 5.3
Ettain Group Member
Business Acquisition [Line Items]
Aggregate cash consideration paid					$ 930.9
Draw on revolving credit facility					150.0
Working capital adjustments							$ 3.4
Revenues from services				$ 182.7						21,269.1
Ettain Group Member | Selling and Administrative Expenses
Business Acquisition [Line Items]
Acquisitions and integration costs										$ 18.8
Ettain Group Member | Acquired Interests Member
Business Acquisition [Line Items]
Aggregate cash consideration paid					925.0
Ettain Group Member | Working Capital And Cash Member
Business Acquisition [Line Items]
Aggregate cash consideration paid					$ 5.9

[1] Balances were net of accumulated impairment loss of $694.2 ($177.0 related to Northern Europe, $3.8 related to APME, $235.2 related to Right Management and $278.2 related to Corporate) as of December 31, 2022; and $749.3 ($232.1 related to Northern Europe, $3.8 related to APME, $235.2 related to Right Management and $278.2 related to Corporate) as of December 31, 2023.

[2] (a) The United States revenues above represent revenues from our company-owned branches and franchise fees received from our franchise operations, which were $11.9, $12.8 and $12.8 for 2023, 2022, and 2021, respectively.