SEGMENT AND CUSTOMER REPORTING - Schedule of Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Total segment income	$ 272.1	$ 128.8
Finance costs	16.0	13.7
Miscellaneous expense (income)	(0.2)	1.4
Employee SBC expense	30.5	26.0
TRS fair value adjustment (TRS FVA): losses	17.0	19.1
Restructuring and other charges (recoveries)	(4.4)	3.9
Earnings before income taxes	256.3	113.7
Operating Segments
Segment Reporting Information [Line Items]
Total segment income	325.2	187.8
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment
Segment Reporting Information [Line Items]
Finance costs	16.0	13.7
Miscellaneous expense (income)	(0.2)	1.4
Employee SBC expense	30.5	26.0
TRS fair value adjustment (TRS FVA): losses	17.0	19.1
Amortization of intangible assets (excluding computer software)	10.0	10.0
Restructuring and other charges (recoveries)	(4.4)	3.9
ATS \| Operating Segments
Segment Reporting Information [Line Items]
Total segment income	$ 48.0	$ 40.7
Segment margin, percentage	6.00%	5.00%
CCS \| Operating Segments
Segment Reporting Information [Line Items]
Total segment income	$ 277.2	$ 147.1
Segment margin, percentage	8.60%	8.00%

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