Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Unamortized Intangible Assets (Advanced Materials & Structures)
Amortization expense of intangible assets	$ 5.1	$ 5.2	$ 10.2	$ 10.4
Estimated average amortization, remainder of year	19.9		19.9
Estimated average amortization, year two	19.9		19.9
Estimated average amortization, year three	19.9		19.9
Estimated average amortization, year four	19.9		19.9
Estimated average amortization, year five	19.9		19.9
Advanced Materials & Structures
Amortized Intangible Assets
Gross Carrying Amount	336.5		336.5		$ 336.5
Accumulated Amortization	72.0		72.0		61.8
Accumulated Impairments	20.7		20.7		20.7
Accumulated Foreign Exchange	1.5		1.5		1.2
Net Carrying Amount	242.3		242.3		252.8
Advanced Materials & Structures \| Trade names
Amortized Intangible Assets
Accumulated Impairments	0.1		0.1		0.1
Accumulated Foreign Exchange	(0.1)		(0.1)		(0.1)
Unamortized Intangible Assets (Advanced Materials & Structures)
Gross Carrying Amount	20.0		20.0		20.0
Net Carrying Amount	20.0		20.0		20.0
Advanced Materials & Structures \| Customer relationships
Amortized Intangible Assets
Gross Carrying Amount	276.3		276.3		276.3
Accumulated Amortization	59.1		59.1		50.4
Accumulated Impairments	0.0		0.0		0.0
Accumulated Foreign Exchange	0.9		0.9		0.7
Net Carrying Amount	216.3		216.3		225.2
Advanced Materials & Structures \| Developed technology
Amortized Intangible Assets
Gross Carrying Amount	34.0		34.0		34.0
Accumulated Amortization	9.7		9.7		8.5
Accumulated Impairments	0.0		0.0		0.0
Accumulated Foreign Exchange	0.3		0.3		0.2
Net Carrying Amount	24.0		24.0		25.3
Advanced Materials & Structures \| Trade names
Amortized Intangible Assets
Gross Carrying Amount	21.8		21.8		21.8
Accumulated Amortization	0.8		0.8		0.8
Accumulated Impairments	20.7		20.7		20.7
Accumulated Foreign Exchange	0.3		0.3		0.3
Net Carrying Amount	0.0		0.0		0.0
Advanced Materials & Structures \| Non-compete agreements
Amortized Intangible Assets
Gross Carrying Amount	2.9		2.9		2.9
Accumulated Amortization	2.0		2.0		1.7
Accumulated Impairments	0.0		0.0		0.0
Accumulated Foreign Exchange	0.0		0.0		0.0
Net Carrying Amount	0.9		0.9		1.2
Advanced Materials & Structures \| Patents
Amortized Intangible Assets
Gross Carrying Amount	1.5		1.5		1.5
Accumulated Amortization	0.4		0.4		0.4
Accumulated Impairments	0.0		0.0		0.0
Accumulated Foreign Exchange	0.0		0.0		0.0
Net Carrying Amount	$ 1.1		$ 1.1		$ 1.1

Indefinite-Lived Intangible Assets (Excluding Goodwill), Gross

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Intangible Assets, Accumulated Foreign Exchange Gain (Loss)

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Intangible Assets, Accumulated Impairment Loss

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

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