Other (Income)/Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Other Income and Expenses [Abstract]
Interest income on corporate funds	$ (96.8)	$ (83.9)	$ (198.3)	$ (175.5)
Realized (gains)/losses on available-for-sale securities, net	0.3	0.6	(1.2)	0.8
Gain on sale of assets	0.0	0.0	0.0	(2.4)
Non-service components of pension income, net	(7.1)	(7.8)	(14.2)	(15.7)
Net (gain)/loss on ADP Ventures' investments	(2.2)	0.0	(2.2)	0.0
Other (income)/loss, net	$ (105.8)	$ (91.1)	$ (215.9)	$ (192.8)