Segment Information - Schedule of Operating Segment Reporting Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total sales		$ 333.8	$ 286.9	$ 964.4	$ 1,206.6
Other operating expense		0.8	15.8	16.0	43.6
Operating income (loss)		22.8	(37.6)	28.8	34.5
Depreciation and amortization		33.7	35.6	102.4	106.0
Stock-based compensation		2.9	0.3	16.2	13.0
Accrual basis additions to capital expenditures		6.5	6.0	14.3	39.4
Corporate & Other and Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	[1]	(15.4)	(8.5)	(44.6)	(49.6)
Other operating expense	[1]	0.0	(0.6)	0.2	15.4
Operating income (loss)	[1]	(13.7)	1.7	(50.2)	(43.8)
Depreciation and amortization	[1]	0.0		0.1	0.1
Stock-based compensation	[1]	2.1	(1.7)	13.7	5.5
Accrual basis additions to capital expenditures	[1]	0.0
Composite Materials
Segment Reporting Information [Line Items]
Total sales		254.1	215.7	732.2	960.4
Composite Materials | Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales		15.0	7.8	42.8	48.0
Composite Materials | Operating Segments
Segment Reporting Information [Line Items]
Total sales		269.1	223.5	775.0	1,008.4
Other operating expense		0.8	16.4	16.3	25.5
Operating income (loss)		30.0	(36.6)	61.9	75.0
Depreciation and amortization		30.1	31.7	91.4	94.3
Stock-based compensation		0.7	1.5	2.1	5.9
Accrual basis additions to capital expenditures		3.7	4.7	10.7	35.4
Engineered Products
Segment Reporting Information [Line Items]
Total sales		79.7	71.2	232.2	246.2
Engineered Products | Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales		0.4	0.7	1.8	1.6
Engineered Products | Operating Segments
Segment Reporting Information [Line Items]
Total sales		80.1	71.9	234.0	247.8
Other operating expense		0.0		(0.5)	2.7
Operating income (loss)		6.5	(2.7)	17.1	3.3
Depreciation and amortization		3.6	3.9	10.9	11.6
Stock-based compensation		0.1	0.5	0.4	1.6
Accrual basis additions to capital expenditures		$ 2.8	$ 1.3	$ 3.6	$ 4.0

[1] We do not allocate corporate expenses to the operating segments.