Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 217.8	$ 203.2
Architectural Specialties [Member]
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	217.6	203.0
Mineral Fiber [Member]
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 0.2	$ 0.2

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details