Accumulated Other Comprehensive Income (Loss) (Reclassification out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold		$ 165.4	$ 162.6	$ 484.7	$ 485.0
Net sales		277.1	260.5	791.2	736.4
Interest expense		11.7	9.9	31.6	28.9
Total loss, before tax		(106.7)	(80.6)	(239.6)	(195.3)
Tax impact		16.0	16.4	48.8	42.3
Total loss, net of tax		(73.2)	(76.2)	(166.8)	(151.3)
Total expense from continuing operations, net of tax		1.9	2.8	6.2	8.5
Total expense from discontinued operations, net of tax expense of $-, ($0.1), $- and ($0.1)			0.2		0.3
Adjustments related to Sale to Knauf		3.5		3.5
Foreign currency translation adjustments related to Sale to Knauf	[1]	81.2		81.2
Total reclassifications for the period		87.0	3.2	92.1	10.2
Derivative Gain (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period		0.4	0.2	1.2	1.4
Derivative Gain (Loss) [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total loss, before tax		0.5	0.2	1.5	1.8
Tax impact		(0.1)		(0.3)	(0.4)
Total loss, net of tax		0.4	0.2	1.2	1.4
Derivative Gain (Loss) [Member] | Natural Gas Commodity Contracts [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold					0.4
Derivative Gain (Loss) [Member] | Foreign Exchange Contracts - Purchases [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold			(0.1)
Derivative Gain (Loss) [Member] | Foreign Exchange Contracts - Sales [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net sales					0.3
Derivative Gain (Loss) [Member] | Interest Rate Swap Contracts [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense		0.5	0.3	1.5	1.1
Prior Service Cost Amortization [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other non-operating (income), net		(0.1)		(0.1)
Amortization Of Net Actuarial Loss [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other non-operating (income), net		2.7	3.6	8.0	10.8
Pension And Postretirement Adjustments [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period		5.4	3.0	9.7	8.8
Pension And Postretirement Adjustments [Member] | Reclassified From Accumulated Other Comprehensive (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total expense, before tax		2.6	3.6	7.9	10.8
Tax impact		(0.7)	(0.8)	(1.7)	(2.3)
Total expense, net of tax		$ 5.4	$ 3.0	$ 9.7	$ 8.8

[1]   (2) Represents estimated amounts reclassified out of Accumulated other comprehensive loss as of September 30, 2019 concurrent with the Sale and included as a component of (Loss) gain from disposal of discontinued operations on the Condensed Consolidated Statement of Earnings and Comprehensive Income. A portion of these amounts were included in our previously reported estimated loss on sale. See Note 5 for additional details.