Interim Financial Data by Segment (Financial Data By Strategic Business Unit Segment) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 4,927.8	$ 4,513.0	$ 13,534.4	$ 12,370.6
Earnings before Income Taxes	1,364.0	1,189.9	3,432.0	3,000.7
Employer Services
Segment Reporting Information [Line Items]
Revenues	3,339.1	3,002.0	9,021.3	8,244.8
Earnings before Income Taxes	1,244.5	1,095.7	3,042.6	2,697.0
PEO Services
Segment Reporting Information [Line Items]
Revenues	1,592.0	1,513.8	4,524.7	4,136.7
Earnings before Income Taxes	261.0	227.2	747.0	632.9
Other
Segment Reporting Information [Line Items]
Revenues	(3.3)	(2.8)	(11.6)	(10.9)
Earnings before Income Taxes	$ (141.5)	$ (133.0)	$ (357.6)	$ (329.2)