Segment Results (Tables)

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

Schedule of Net Sales

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
Net sales
Mineral Fiber	$	214.5	$	187.3	$	611.3	$	542.9
Architectural Specialties		77.7		59.0		212.8		155.3
Total net sales	$	292.2	$	246.3	$	824.1	$	698.2

Schedule of Segment Operating Income (Loss)

	Three Months Ended					Nine Months Ended
	September 30,					September 30,
	2021			2020		2021			2020
Segment operating income (loss)
Mineral Fiber	$	68.5		$	58.1	$	201.2		$	173.7
Architectural Specialties		5.0			9.1		7.5			20.9
Unallocated Corporate		(1.4	)		5.1		(4.2	)		16.1
Total consolidated operating income	$	72.1		$	72.3	$	204.5		$	210.7

Reconciliation of Total Consolidated Operating Income to Earnings Before Income Taxes

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2021			2020			2021			2020
Total consolidated operating income	$	72.1		$	72.3		$	204.5		$	210.7
Interest expense		6.1			6.1			17.4			18.7
Other non-operating (income) expense, net		(1.4	)		(3.2	)		(4.3	)		361.8
Earnings (loss) from continuing operations before income taxes	$	67.4		$	69.4		$	191.4		$	(169.8	)

Reconciliation of Total Segment Assets to Total Consolidated Assets

	September 30, 2021		December 31, 2020
Segment assets
Mineral Fiber	$	1,119.9	$	1,101.1
Architectural Specialties		365.4		357.7
Unallocated Corporate		219.6		259.7
Total consolidated assets	$	1,704.9	$	1,718.5