Goodwill And Intangible Assets, Net - Changes in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Goodwill [Roll Forward]
Beginning balance	$ 2,353.6	$ 2,339.4
Additions and other adjustments	887.0	24.4
Currency translation adjustments	32.9	(10.2)
Ending balance	3,273.5	2,353.6
Employer Services
Goodwill [Roll Forward]
Beginning balance	2,348.8	2,334.6
Additions and other adjustments	887.0	24.4
Currency translation adjustments	32.9	(10.2)
Ending balance	3,268.7	2,348.8
PEO Services
Goodwill [Roll Forward]
Beginning balance	4.8	4.8
Additions and other adjustments	0.0	0.0
Currency translation adjustments	0.0	0.0
Ending balance	$ 4.8	$ 4.8