v3.26.1
Business Combinations, Goodwill by Segment (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Goodwill [Roll Forward]    
Goodwill $ 4,707.3 $ 4,611.3
Goodwill Additions, net of adjustments 37.4 6.6
Goodwill, Divestiture (3.7)  
Goodwill, Translation Adjustments (14.3) 97.9
Goodwill 4,726.7 4,715.8
Leasing Advisory    
Goodwill [Roll Forward]    
Goodwill 1,405.3 1,372.6
Goodwill Additions, net of adjustments 0.0 0.0
Goodwill, Divestiture 0.0  
Goodwill, Translation Adjustments (4.9) 35.4
Goodwill 1,400.4 1,408.0
Capital Markets Services    
Goodwill [Roll Forward]    
Goodwill 2,019.8 1,971.5
Goodwill Additions, net of adjustments 0.0 6.6
Goodwill, Divestiture 0.0  
Goodwill, Translation Adjustments (6.5) 44.5
Goodwill 2,013.3 2,022.6
Real Estate Management Services    
Goodwill [Roll Forward]    
Goodwill 1,225.1 1,211.3
Goodwill Additions, net of adjustments 37.4 0.0
Goodwill, Divestiture (3.7)  
Goodwill, Translation Adjustments (2.7) 16.4
Goodwill 1,256.1 1,227.7
Software and Technology Solutions    
Goodwill [Roll Forward]    
Goodwill Additions, net of adjustments 0.0 0.0
Goodwill, Divestiture 0.0  
Investment Management    
Goodwill [Roll Forward]    
Goodwill 57.1 55.9
Goodwill, Translation Adjustments (0.2) 1.6
Goodwill $ 56.9 $ 57.5