Goodwill and Intangible Assets, net - Changes In Goodwill (Details) $ in Millions	3 Months Ended
	Sep. 30, 2023 USD ($)
Goodwill [Roll Forward]
Balance at June 30, 2023	$ 2,339.4
Additions and other adjustments	27.5
Currency translation adjustments	(14.4)
Balance at September 30, 2023	2,352.5
Employer Services
Goodwill [Roll Forward]
Balance at June 30, 2023	2,334.6
Additions and other adjustments	27.5
Currency translation adjustments	(14.4)
Balance at September 30, 2023	2,347.7
PEO Services
Goodwill [Roll Forward]
Balance at June 30, 2023	4.8
Additions and other adjustments	0.0
Currency translation adjustments	0.0
Balance at September 30, 2023	$ 4.8