Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 15,005.4	$ 14,589.8	$ 14,110.2
HCM
Disaggregation of Revenue [Line Items]
Revenues	6,629.1	6,540.9	6,441.8
HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	2,694.8	2,543.2	2,444.4
PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	3,092.0	2,907.7	2,647.5
Global
Disaggregation of Revenue [Line Items]
Revenues	2,167.1	2,052.8	2,014.6
Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	422.4	545.2	561.9
Employer Services
Disaggregation of Revenue [Line Items]
Revenues	10,195.2	10,086.6	9,942.8
Employer Services | HCM
Disaggregation of Revenue [Line Items]
Revenues	6,634.6	6,546.4	6,447.5
Employer Services | HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	975.0	947.2	924.0
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	2,167.1	2,052.8	2,014.6
Employer Services | Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	418.5	540.2	556.7
PEO
Disaggregation of Revenue [Line Items]
Revenues	4,818.3	4,511.5	4,177.7
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	1,722.4	1,598.8	1,525.0
PEO | PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	3,092.0	2,907.7	2,647.5
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	3.9	5.0	5.2
Other
Disaggregation of Revenue [Line Items]
Revenues	(8.1)	(8.3)	(10.3)
Other | HCM
Disaggregation of Revenue [Line Items]
Revenues	(5.5)	(5.5)	(5.7)
Other | HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	(2.6)	(2.8)	(4.6)
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