v3.26.1
Goodwill and Intangible Assets (Narrative) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Indefinite-Lived Intangible Assets [Line Items]    
Goodwill $ 259.2 $ 217.8
Architectural Specialties [Member]    
Indefinite-Lived Intangible Assets [Line Items]    
Goodwill 259.0 217.6
Mineral Fiber [Member]    
Indefinite-Lived Intangible Assets [Line Items]    
Goodwill $ 0.2 $ 0.2