Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 18,012.2	$ 16,498.3	$ 15,005.4
HCM
Disaggregation of Revenue [Line Items]
Revenues	7,716.1	7,174.9	6,655.2
HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	3,386.0	3,116.3	2,690.9
PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	3,800.9	3,514.4	3,092.0
Global
Disaggregation of Revenue [Line Items]
Revenues	2,295.8	2,240.9	2,144.9
Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	813.4	451.8	422.4
Employer Services
Disaggregation of Revenue [Line Items]
Revenues	12,042.6	10,967.7	10,195.2
Employer Services | HCM
Disaggregation of Revenue [Line Items]
Revenues	7,724.7	7,183.1	6,660.7
Employer Services | HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	1,216.1	1,096.1	971.1
Employer Services | PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0	0.0
Employer Services | Global
Disaggregation of Revenue [Line Items]
Revenues	2,295.8	2,240.9	2,144.9
Employer Services | Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	806.0	447.6	418.5
PEO
Disaggregation of Revenue [Line Items]
Revenues	5,984.2	5,545.7	4,818.3
PEO | HCM
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0	0.0
PEO | HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	2,175.9	2,027.1	1,722.4
PEO | PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	3,800.9	3,514.4	3,092.0
PEO | Global
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0	0.0
PEO | Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	7.4	4.2	3.9
Other
Disaggregation of Revenue [Line Items]
Revenues	(14.6)	(15.1)	(8.1)
Other | HCM
Disaggregation of Revenue [Line Items]
Revenues	(8.6)	(8.2)	(5.5)
Other | HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	(6.0)	(6.9)	(2.6)
Other | PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0	0.0
Other | Global
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0	0.0
Other | Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	$ 0.0	$ 0.0	$ 0.0