Business Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Number of business segments | segment			2
Segment Reporting Information [Line Items]
Retirement Benefit Expense	$ 19.3	$ 23.8	$ 57.8	$ 71.8
Sales	832.7	1,069.6	2,980.7	3,175.9
Operating profit (loss):	(73.0)	59.9	14.3	129.8
LIFO and net realizable value reserves	0.2	10.0	0.0	12.9
Corporate expenses	(10.7)	(11.4)	(33.6)	(37.3)
Closed company and other expenses	(6.5)	(9.2)	(18.6)	(22.1)
Interest expense, net	(27.5)	(25.2)	(81.0)	(82.8)
Income (loss) from continuing operations before income tax provision (benefit)	(117.9)	4.1	(118.9)	(25.3)
High Performance Materials & Components
Segment Reporting Information [Line Items]
Total sales:	474.7	507.7	1,528.6	1,506.2
Operating profit (loss):	18.8	53.8	136.1	162.5
Flat Rolled Products
Segment Reporting Information [Line Items]
Total sales:	358.0	561.9	1,452.1	1,669.7
Operating profit (loss):	(91.8)	6.1	(121.8)	(32.7)
Operating Segments
Segment Reporting Information [Line Items]
Retirement Benefit Expense	17.7	20.7	53.2	62.4
Total sales:	867.9	1,114.1	3,104.5	3,309.7
Operating Segments | High Performance Materials & Components
Segment Reporting Information [Line Items]
Retirement Benefit Expense	3.0	5.1	9.1	15.6
Total sales:	490.1	527.1	1,588.5	1,562.6
Operating Segments | Flat Rolled Products
Segment Reporting Information [Line Items]
Retirement Benefit Expense	14.7	15.6	44.1	46.8
Total sales:	377.8	587.0	1,516.0	1,747.1
Intersegment Sales
Segment Reporting Information [Line Items]
Total sales:	35.2	44.5	123.8	133.8
Intersegment Sales | High Performance Materials & Components
Segment Reporting Information [Line Items]
Total sales:	15.4	19.4	59.9	56.4
Intersegment Sales | Flat Rolled Products
Segment Reporting Information [Line Items]
Total sales:	19.8	25.1	63.9	77.4
Non-Segment | Corporate expenses
Segment Reporting Information [Line Items]
Retirement Benefit Expense	1.0	1.3	2.9	4.0
Non-Segment | Closed company and other expenses
Segment Reporting Information [Line Items]
Retirement Benefit Expense	$ 0.6	$ 1.8	$ 1.7	$ 5.4