Business Segments (Details8) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Inventory valuation reserves		$ 70,900,000	$ 65,400,000
Segment EBITDA		623,800,000	351,600,000	$ 244,600,000
Corporate expenses		(62,400,000)	(55,900,000)	(40,900,000)
Closed operations and other expenses		(12,100,000)	(4,800,000)	(7,400,000)
Depreciation and amortization		(142,900,000)	(143,900,000)	(143,300,000)
Interest expense, net		(87,400,000)	(96,900,000)	(94,400,000)
Restructuring and other credits (charges)		(23,700,000)	10,500,000	(1,132,100,000)
Strike related costs		$ 0	(63,200,000)	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Settlement Gain (Loss), Statement Of Income Or Comprehensive Income, Extensible Enumeration, Not Disclosed Flag		Retirement benefit settlement gain (See Note 14)
Settlement gain		$ 0	64,900,000	0
Impairment of goodwill		0	0	(287,000,000)
Joint venture restructuring credit (charge)		900,000	0	(2,400,000)
Debt extinguishment charge		0	(65,500,000)	(21,500,000)
Gain (loss) on asset sales and sale of business, net		(134,200,000)	13,800,000	2,500,000
Income (loss) before income taxes		162,000,000.0	10,600,000	(1,481,900,000)
High Performance Materials & Components
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Strike related costs			3,500,000
Impairment of goodwill	$ 0	0	0
Various AA&S Segment Operations
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Strike related costs			59,700,000
Operating Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Depreciation and amortization		(142,900,000)	(143,900,000)	(143,300,000)
Operating Segments | High Performance Materials & Components
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Segment EBITDA		296,000,000.0	159,900,000	129,600,000
Depreciation and amortization		(68,300,000)	(75,000,000.0)	(78,100,000)
Operating Segments | Advanced Alloys & Solutions [Member]
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Segment EBITDA		327,800,000	191,700,000	115,000,000.0
Depreciation and amortization		$ (67,400,000)	$ (64,500,000)	$ (62,100,000)