v3.26.1
Revenue (Schedule of Net Sales by Major Customer Channel within Each Segment) (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Entity Wide Revenue Major Customer [Line Items]        
Net sales $ 472.0 $ 424.6 $ 881.9 $ 807.3
Mineral Fiber [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 288.2 267.0 545.4 512.1
Mineral Fiber [Member] | Distributors [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 217.9 200.2 406.2 380.2
Mineral Fiber [Member] | Home Centers [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 27.3 25.0 57.5 52.0
Mineral Fiber [Member] | Direct Customers [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 17.9 17.9 30.8 32.0
Mineral Fiber [Member] | Other [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 25.1 23.9 50.9 47.9
Architectural Specialties [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 183.8 157.6 336.5 295.2
Architectural Specialties [Member] | Distributors [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 80.6 70.0 147.0 124.3
Architectural Specialties [Member] | Direct Customers [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales 96.4 80.9 177.0 158.3
Architectural Specialties [Member] | Other [Member]        
Entity Wide Revenue Major Customer [Line Items]        
Net sales $ 6.8 $ 6.7 $ 12.5 $ 12.6