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Goodwill and Identifiable Assets (Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2026	Jun. 30, 2026	Jun. 30, 2025
Goodwill [Roll Forward]
Beginning balance	$ 2,143.2	$ 2,143.2	$ 1,893.1
Translation adjustment	1.4	(0.2)
Ending balance		2,280.4
Commercial
Goodwill [Roll Forward]
Beginning balance	1,324.9	1,324.9	1,074.8
Translation adjustment	1.4	(0.2)
Ending balance		1,462.1
Federal Government
Goodwill [Roll Forward]
Beginning balance	818.3	818.3	818.3
Ending balance		818.3
2025 Acquisitions [Member] \| Commercial
Goodwill [Roll Forward]
Goodwill, Acquired During Period	$ 248.7
2026 Acquisitions [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period		137.4	$ 248.7
2026 Acquisitions [Member] \| Commercial
Goodwill [Roll Forward]
Goodwill, Acquired During Period		$ 137.4