Goodwill and Other Intangible Assets - Changes in Carrying Value of Goodwill by Reportable Segment (Details) $ in Millions	9 Months Ended
	Sep. 30, 2025 USD ($)
Goodwill [Roll Forward]
Balance, December 31, 2024	$ 1,563.4	[1]
Acquisitions	0.9
Dispositions	(0.7)
Impairment charges	(58.1)
Currency impact	38.4
Balance, June 30, 2025	1,543.9	[1]
Reportable segments | Americas
Goodwill [Roll Forward]
Balance, December 31, 2024	1,048.2	[2]
Acquisitions	0.0	[2]
Dispositions	0.0	[2]
Impairment charges	0.0	[2]
Currency impact	1.4	[2]
Balance, June 30, 2025	1,049.6	[2]
Reportable segments | Southern Europe
Goodwill [Roll Forward]
Balance, December 31, 2024	145.3	[3]
Acquisitions	0.0	[3]
Dispositions	0.0	[3]
Impairment charges	(24.7)	[3]
Currency impact	18.7	[3]
Balance, June 30, 2025	139.3	[3]
Reportable segments | Northern Europe
Goodwill [Roll Forward]
Balance, December 31, 2024	181.4
Acquisitions	0.0
Dispositions	(0.7)
Impairment charges	(33.4)
Currency impact	16.8
Balance, June 30, 2025	164.1
Reportable segments | APME
Goodwill [Roll Forward]
Balance, December 31, 2024	63.0
Acquisitions	0.9
Dispositions	0.0
Impairment charges	0.0
Currency impact	1.5
Balance, June 30, 2025	65.4
Corporate
Goodwill [Roll Forward]
Balance, December 31, 2024	125.5	[4]
Acquisitions	0.0	[4]
Dispositions	0.0	[4]
Impairment charges	0.0	[4]
Currency impact	0.0	[4]
Balance, June 30, 2025	$ 125.5	[4]

[1] Balances were net of accumulated impairment loss of $807.4 and $749.3 as of September 30, 2025 and December 31, 2024, respectively.

[2] Balances related to the United States were $1,007.2 as of both December 31, 2024 and September 30, 2025.

[3] Balances related to France were $70.9 and $80.4 as of December 31, 2024 and September 30, 2025, respectively. Balances related to Italy were $3.5 and $4.0 as of December 31, 2024 and September 30, 2025, respectively

[4] The majority of the Corporate balance relates to goodwill attributable to our acquisitions of Right Management ($62.1) and Jefferson Wells ($55.5). Jefferson Wells is part of the United States reporting unit. Right Management is allocated to the reporting units of the countries in which Right Management operates. For purposes of monitoring our total assets by segment, we do not allocate the Corporate balances to the respective reportable segments as this is commensurate with how we operate our business. We do, however, include these balances within the appropriate reporting units for our goodwill impairment testing.