SEGMENT AND CUSTOMER REPORTING - Schedule of Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Total segment income	$ 325.0	$ 138.0	$ 726.3	$ 396.7
Finance costs	12.8	11.2	40.0	40.2
Miscellaneous expense	1.3	2.8	4.4	13.8
Employee SBC expense	15.6	12.7	56.8	47.3
TRS fair value adjustment (TRS FVA): losses (gains)	(113.3)	7.7	(191.6)	(39.5)
Amortization of intangible assets (excluding computer software)	11.4	11.1	33.6	32.0
Restructuring and other charges, net of recoveries	4.9	1.0	23.3	17.3
Earnings before income taxes	310.9	124.0	681.9	342.7
Operating Segments
Segment Reporting Information [Line Items]
Total segment income	242.2	168.8	644.7	449.0
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment
Segment Reporting Information [Line Items]
Finance costs	12.8	11.2	40.0	40.2
Miscellaneous expense	1.3	2.8	4.4	13.8
Foreign currency forward contracts transitional adjustments	0.0	(0.5)	0.0	(1.7)
Employee SBC expense	15.6	12.7	56.8	47.3
TRS fair value adjustment (TRS FVA): losses (gains)	(113.3)	7.7	(191.6)	(39.5)
Amortization of intangible assets (excluding computer software)	10.0	9.9	29.9	28.9
Restructuring and other charges, net of recoveries	4.9	1.0	23.3	17.3
ATS | Operating Segments
Segment Reporting Information [Line Items]
Total segment income	$ 42.8	$ 40.1	$ 127.0	$ 107.1
Segment margin, percentage	5.50%	4.90%	5.30%	4.60%
CCS | Operating Segments
Segment Reporting Information [Line Items]
Total segment income	$ 199.4	$ 128.7	$ 517.7	$ 341.9
Segment margin, percentage	8.30%	7.60%	8.20%	7.20%