Other (Income)/Expense, Net - Summary of Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2024
Other Income, Net [Abstract]
Interest income on corporate funds	$ (371.0)	$ (319.5)	$ (241.3)
Realized (gains)/losses on available-for-sale securities, net	(2.9)	1.7	5.9
Gain on sale of assets	0.0	(5.0)	(17.1)
Non-service components of pension income, net	(28.3)	(31.3)	(34.2)
Net (gain)/loss on ADP Ventures' investments	(8.4)	0.0	0.0
Other (income)/expense, net	$ (410.6)	$ (354.1)	$ (286.7)