Segment Results (Schedule of Net Sales) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Total net sales	$ 365.1	$ 325.4	$ 691.4	$ 635.6
Mineral Fiber [Member]
Segment Reporting Information [Line Items]
Total net sales	250.2	234.0	489.8	462.4
Architectural Specialties [Member]
Segment Reporting Information [Line Items]
Total net sales	$ 114.9	$ 91.4	$ 201.6	$ 173.2

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details