Business Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Sales	$ 955.5	$ 1,004.8
Operating profit (loss)	81.2	61.7
LIFO and net realizable value reserves	0.0	(0.1)
Corporate expenses	(12.8)	(16.6)
Closed operations and other expenses	(6.6)	(3.1)
Gain on asset sales, net	2.5	0.0
Restructuring and other charges	(8.0)	0.0
Interest expense, net	(21.9)	(24.8)
Income from Continuing Operations before Income Taxes, Noncontrolling Interest	34.4	17.1
Operating Segments
Segment Reporting Information [Line Items]
Sales	1,036.1	1,088.5
Operating Segments | High Performance Materials & Components
Segment Reporting Information [Line Items]
Sales	448.5	516.3
Operating profit (loss)	57.1	51.7
Operating Segments | Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Sales	587.6	572.2
Operating profit (loss)	24.1	10.0
Internal Customers | Operating Segments
Segment Reporting Information [Line Items]
Sales	80.6	83.7
Internal Customers | Operating Segments | High Performance Materials & Components
Segment Reporting Information [Line Items]
Sales	28.2	19.7
Internal Customers | Operating Segments | Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Sales	52.4	64.0
External Customers | Operating Segments
Segment Reporting Information [Line Items]
Sales	955.5	1,004.8
External Customers | Operating Segments | High Performance Materials & Components
Segment Reporting Information [Line Items]
Sales	420.3	496.6
External Customers | Operating Segments | Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Sales	$ 535.2	$ 508.2