Goodwill and Other Intangible Assets - Changes in Carrying Value of Goodwill by Reportable Segment (Details) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($)
Goodwill [Roll Forward]
Balance, December 31, 2021	$ 1,722.2	[1]
Acquisitions	(4.6)	[2]
Currency impact	(47.7)
Balance, June 30, 2022	1,669.9	[1]
Reportable segments | Americas
Goodwill [Roll Forward]
Balance, December 31, 2021	1,058.9	[3]
Acquisitions	(4.6)	[2],[3]
Currency impact	(1.1)	[3]
Balance, June 30, 2022	1,053.2	[3]
Reportable segments | Southern Europe
Goodwill [Roll Forward]
Balance, December 31, 2021	146.7	[4]
Acquisitions	0.0	[2],[4]
Currency impact	(10.6)	[4]
Balance, June 30, 2022	136.1	[4]
Reportable segments | Northern Europe
Goodwill [Roll Forward]
Balance, December 31, 2021	313.7
Acquisitions	0.0	[2]
Currency impact	(29.3)
Balance, June 30, 2022	284.4
Reportable segments | APME
Goodwill [Roll Forward]
Balance, December 31, 2021	76.9
Acquisitions	0.0	[2]
Currency impact	(6.7)
Balance, June 30, 2022	70.2
Corporate
Goodwill [Roll Forward]
Balance, December 31, 2021	126.0	[5]
Acquisitions	0.0	[2],[5]
Currency impact	0.0	[5]
Balance, June 30, 2022	$ 126.0	[5]

[1] Balances were net of accumulated impairment loss of $644.2 as of both June 30, 2022 and December 31, 2021.

[2] Represents post-closing working capital adjustments related to the United States Experis acquisition. See Note 5 to the Consolidated Financial Statements for further information.

[3] Balances related to the United States were $1,013.0 and $1,008.3 as of December 31, 2021 and June 30, 2022, respectively.

[4] Balances related to France were $68.2 and $62.9 as of December 31, 2021 and June 30, 2022, respectively. Balances related to Italy were $3.9 and $3.6 as of December 31, 2021 and June 30, 2022, respectively.

[5] 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. See table below for the breakout of goodwill balances by reporting unit.