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GOODWILL (Goodwill by Segment) (Details) - USD ($) $ in Millions		1 Months Ended		12 Months Ended
	May 24, 2021	Dec. 31, 2023	Apr. 30, 2022	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 2,314.8	$ 2,321.0
Acquisitions, including measurement period adjustments				62.8	10.5
Effect of foreign currency translation				8.6	(16.7)
Goodwill, ending balance		$ 2,386.2		2,386.2	2,314.8
Homes.com
Goodwill [Roll Forward]
Goodwill, ending balance	$ 91.9
Business Immo
Goodwill [Roll Forward]
Goodwill acquired			$ 7.1
North America
Goodwill [Roll Forward]
Goodwill, beginning balance				2,149.2	2,145.8
Acquisitions, including measurement period adjustments				0.0	3.4
Effect of foreign currency translation				0.0	0.0
Goodwill, ending balance		2,149.2		2,149.2	2,149.2
North America | Homes.com
Goodwill [Roll Forward]
Goodwill acquired	$ 91.9
Goodwill measuring period adjustment					3.4
North America | OnTheMarket
Goodwill [Roll Forward]
Goodwill acquired		62.8
International
Goodwill [Roll Forward]
Goodwill, beginning balance				165.6	175.2
Acquisitions, including measurement period adjustments				62.8	7.1
Effect of foreign currency translation				8.6	(16.7)
Goodwill, ending balance		$ 237.0		237.0	165.6
International | Business Immo
Goodwill [Roll Forward]
Goodwill acquired					$ 7.1
International | OnTheMarket
Goodwill [Roll Forward]
Goodwill acquired				$ 62.8

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