Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 4,215.6	$ 3,832.3
Employer Services
Disaggregation of Revenue [Line Items]
Revenues	2,790.2	2,571.5
PEO Services
Disaggregation of Revenue [Line Items]
Revenues	1,429.4	1,264.1
Other
Disaggregation of Revenue [Line Items]
Revenues	(4.0)	(3.3)
HCM
Disaggregation of Revenue [Line Items]
Revenues	1,811.0	1,666.7
HCM | Employer Services
Disaggregation of Revenue [Line Items]
Revenues	1,813.2	1,669.1
HCM | PEO Services
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0
HCM | Other
Disaggregation of Revenue [Line Items]
Revenues	(2.2)	(2.4)
HRO, excluding PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	777.3	679.3
HRO, excluding PEO zero-margin benefits pass-throughs | Employer Services
Disaggregation of Revenue [Line Items]
Revenues	296.8	256.2
HRO, excluding PEO zero-margin benefits pass-throughs | PEO Services
Disaggregation of Revenue [Line Items]
Revenues	482.3	424.0
HRO, excluding PEO zero-margin benefits pass-throughs | Other
Disaggregation of Revenue [Line Items]
Revenues	(1.8)	(0.9)
PEO zero-margin benefits pass-throughs
Disaggregation of Revenue [Line Items]
Revenues	945.8	839.5
PEO zero-margin benefits pass-throughs | Employer Services
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0
PEO zero-margin benefits pass-throughs | PEO Services
Disaggregation of Revenue [Line Items]
Revenues	945.8	839.5
PEO zero-margin benefits pass-throughs | Other
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0
Global
Disaggregation of Revenue [Line Items]
Revenues	540.5	545.7
Global | Employer Services
Disaggregation of Revenue [Line Items]
Revenues	540.5	545.7
Global | PEO Services
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0
Global | Other
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0
Interest on funds held for clients
Disaggregation of Revenue [Line Items]
Revenues	141.0	101.1
Interest on funds held for clients | Employer Services
Disaggregation of Revenue [Line Items]
Revenues	139.7	100.5
Interest on funds held for clients | PEO Services
Disaggregation of Revenue [Line Items]
Revenues	1.3	0.6
Interest on funds held for clients | Other
Disaggregation of Revenue [Line Items]
Revenues	$ 0.0	$ 0.0