Segment Information, Net Sales by Product Categories (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Net Sales:
Net sales	$ 371.7	$ 335.1
Aero/HS products
Net Sales:
Net sales	180.3	163.6
Automotive Extrusions
Net Sales:
Net sales	50.1	40.8
GE products
Net Sales:
Net sales	119.1	112.2
Other products
Net Sales:
Net sales	$ 22.2	$ 18.5