Interim Financial Data by Segment - Schedule of Depreciation and Amortization Included in Earnings Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Total depreciation and amortization	$ 145.6	$ 151.0	$ 292.3	$ 289.7
Other
Segment Reporting Information [Line Items]
Total depreciation and amortization	14.6	16.0	29.5	32.4
Employer Services | Operating Segments
Segment Reporting Information [Line Items]
Total depreciation and amortization	130.5	133.3	261.6	253.9
PEO | Operating Segments
Segment Reporting Information [Line Items]
Total depreciation and amortization	$ 0.5	$ 1.7	$ 1.2	$ 3.4