v3.26.1
Interim Financial Data by Segment - Schedule of Revenues, Significant Segment Expenses and Earnings before Income Taxes by Reportable Segments (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2026
Mar. 31, 2025
Segment Reporting Information [Line Items]        
Revenues $ 5,939.2 $ 5,553.0 $ 16,473.6 $ 15,434.1
Less segment expenses:        
Total consolidated earnings before income taxes 1,781.8 1,621.9 4,472.5 4,119.4
Operating Segments        
Less segment expenses:        
Total consolidated earnings before income taxes 1,905.3 1,753.4 4,884.6 4,577.9
Intercompany eliminations        
Segment Reporting Information [Line Items]        
Revenues (2.9) (3.4) (9.7) (9.6)
Operating Segments, Excluding Intersegment Elimination        
Segment Reporting Information [Line Items]        
Revenues 5,942.1 5,556.4 16,483.3 15,443.7
Other        
Less segment expenses:        
Total consolidated earnings before income taxes (123.5) (131.5) (412.1) (458.5)
Employer Services | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 4,036.1 3,767.9 11,134.6 10,417.4
Less segment expenses:        
Selling and marketing 603.0 555.0 1,733.5 1,591.9
Zero-margin benefits pass-through costs 0.0 0.0 0.0 0.0
Worker's compensation coverage and state unemployment taxes 0.0 0.0 0.0 0.0
Other segment expenses 1,775.0 1,712.8 5,235.5 4,978.2
Total consolidated earnings before income taxes 1,658.1 1,500.1 4,165.6 3,847.3
Employer Services | Intercompany eliminations        
Segment Reporting Information [Line Items]        
Revenues (2.9) (3.4) (9.7) (9.6)
Employer Services | Operating Segments, Excluding Intersegment Elimination        
Segment Reporting Information [Line Items]        
Revenues 4,036.1 3,767.9 11,134.6 10,417.4
PEO Services | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 1,906.0 1,788.5 5,348.7 5,026.3
Less segment expenses:        
Selling and marketing 109.5 94.0 304.9 266.1
Zero-margin benefits pass-through costs 1,170.0 1,090.0 3,427.2 3,194.4
Worker's compensation coverage and state unemployment taxes 271.4 252.5 564.8 532.9
Other segment expenses 107.9 98.7 332.8 302.3
Total consolidated earnings before income taxes 247.2 253.3 719.0 730.6
PEO Services | Intercompany eliminations        
Segment Reporting Information [Line Items]        
Revenues 0.0 0.0 0.0 0.0
PEO Services | Operating Segments, Excluding Intersegment Elimination        
Segment Reporting Information [Line Items]        
Revenues 1,906.0 1,788.5 5,348.7 5,026.3
Revenues from external customers | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 5,535.3 5,197.8 15,474.2 14,552.8
Revenues from external customers | Employer Services | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 3,633.0 3,412.6 10,134.7 9,534.6
Revenues from external customers | PEO Services | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 1,902.3 1,785.2 5,339.5 5,018.2
Interest on funds held for clients        
Segment Reporting Information [Line Items]        
Revenues 403.9 355.2 999.4 881.3
Interest on funds held for clients | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 403.9 355.2 999.4 881.3
Interest on funds held for clients | Employer Services | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 400.2 351.9 990.2 873.2
Interest on funds held for clients | PEO Services | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues $ 3.7 $ 3.3 $ 9.2 $ 8.1