Segment Information - Schedule of Operating Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Total sales	$ 286.9	$ 572.5	$ 1,206.6	$ 1,791.4
Other operating expense	15.8		43.6
Operating income (loss)	(37.6)	109.9	34.5	327.8
Depreciation and amortization	35.6	34.4	106.0	107.1
Stock-based compensation	0.3	2.4	13.0	15.9
Accrual basis additions to capital expenditures	6.0	53.3	39.4	160.9
Corporate & Other and Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	(8.5)	(23.3)	(49.6)	(64.1)
Other operating expense	(0.6)		15.4
Operating income (loss)	1.7	(10.5)	(43.8)	(48.0)
Depreciation and amortization			0.1	0.1
Stock-based compensation	(1.7)	1.0	5.5	8.1
Composite Materials
Segment Reporting Information [Line Items]
Total sales	215.7	448.0	960.4	1,419.7
Composite Materials | Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	7.8	23.3	48.0	64.0
Composite Materials | Operating Segments
Segment Reporting Information [Line Items]
Total sales	223.5	471.3	1,008.4	1,483.7
Other operating expense	16.4		25.5
Operating income (loss)	(36.6)	100.1	75.0	324.4
Depreciation and amortization	31.7	30.7	94.3	95.7
Stock-based compensation	1.5	1.2	5.9	6.4
Accrual basis additions to capital expenditures	4.7	51.0	35.4	156.8
Engineered Products
Segment Reporting Information [Line Items]
Total sales	71.2	124.5	246.2	371.7
Engineered Products | Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	0.7		1.6	0.1
Engineered Products | Operating Segments
Segment Reporting Information [Line Items]
Total sales	71.9	124.5	247.8	371.8
Other operating expense			2.7
Operating income (loss)	(2.7)	20.3	3.3	51.4
Depreciation and amortization	3.9	3.7	11.6	11.3
Stock-based compensation	0.5	0.2	1.6	1.4
Accrual basis additions to capital expenditures	$ 1.3	$ 2.3	$ 4.0	$ 4.1