Segment Information - Schedule of Operating Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total sales	$ 378.7	$ 609.0	$ 919.7	$ 1,218.9
Other operating expense	13.1		27.8
Operating income (loss)	6.4	115.1	72.1	217.9
Depreciation and amortization	34.9	34.0	70.4	72.7
Stock-based compensation	(1.7)	2.4	12.7	13.5
Accrual basis additions to capital expenditures	11.5	50.1	33.4	107.6
Corporate & Other and Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	(15.8)	(21.5)	(41.1)	(40.8)
Other operating expense	2.2		16.0
Operating income (loss)	(13.2)	(13.0)	(45.5)	(37.5)
Depreciation and amortization	0.1	0.1	0.1	0.1
Stock-based compensation	(1.3)	0.9	7.2	7.1
Composite Materials
Segment Reporting Information [Line Items]
Total sales	306.2	484.0	744.7	971.7
Composite Materials | Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	15.4	21.5	40.2	40.7
Composite Materials | Operating Segments
Segment Reporting Information [Line Items]
Total sales	321.6	505.5	784.9	1,012.4
Other operating expense	8.5		9.1
Operating income (loss)	20.1	111.8	111.6	224.3
Depreciation and amortization	30.8	30.1	62.6	65.0
Stock-based compensation	(0.3)	1.1	4.4	5.2
Accrual basis additions to capital expenditures	10.5	49.0	30.7	105.8
Engineered Products
Segment Reporting Information [Line Items]
Total sales	72.5	125.0	175.0	247.2
Engineered Products | Intersegment Elimination
Segment Reporting Information [Line Items]
Total sales	0.4		0.9	0.1
Engineered Products | Operating Segments
Segment Reporting Information [Line Items]
Total sales	72.9	125.0	175.9	247.3
Other operating expense	2.4		2.7
Operating income (loss)	(0.5)	16.3	6.0	31.1
Depreciation and amortization	4.0	3.8	7.7	7.6
Stock-based compensation	(0.1)	0.4	1.1	1.2
Accrual basis additions to capital expenditures	$ 1.0	$ 1.1	$ 2.7	$ 1.8