v3.26.3
Revenue (Schedule of Net Sales by Major Customer Channel within Each Segment) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Entity Wide Revenue Major Customer [Line Items]        
Net sales $ 475.8 $ 425.2 $ 1,357.7 $ 1,232.5
Mineral Fiber [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 292.1 274.0 837.5 786.1
Mineral Fiber [Member] | Distributors [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 220.7 205.0 626.9 585.2
Mineral Fiber [Member] | Home Centers [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 29.2 26.6 86.7 78.6
Mineral Fiber [Member] | Direct Customers [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 16.3 15.6 47.1 47.6
Mineral Fiber [Member] | Other [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 25.9 26.8 76.8 74.7
Architectural Specialties [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 183.7 151.2 520.2 446.4
Architectural Specialties [Member] | Distributors [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 82.8 67.3 229.8 191.6
Architectural Specialties [Member] | Direct Customers [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 95.0 76.7 272.0 235.0
Architectural Specialties [Member] | Other [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales $ 5.9 $ 7.2 $ 18.4 $ 19.8