STOCK COMPENSATION PLANS - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	$ 22.3	$ 13.0	$ 59.6	$ 41.9
Income tax benefits	3.1	2.1	8.5	6.4
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	17.2	11.2	46.0	32.5
Selling, general and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	$ 5.1	$ 1.8	$ 13.6	$ 9.4