Segment and Geographical Area Information, Schedule of net sales by end market segment applications (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue from External Customer
Net sales	$ 316.6	$ 336.4	$ 367.2	$ 371.7	$ 338.0	$ 338.9	$ 344.1	$ 335.1	$ 1,391.9	$ 1,356.1	$ 1,297.5
Aero/HS products
Revenue from External Customer
Net sales									695.5	686.3	677.0
Automotive Extrusions
Revenue from External Customer
Net sales									199.2	173.5	129.5
GE products
Revenue from External Customer
Net sales									426.1	419.5	411.0
Other products
Revenue from External Customer
Net sales									$ 71.1	$ 76.8	$ 80.0