Segment Information, Net Sales by End Market Segment Applications (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net Sales:
Net sales			$ 678.1	$ 738.9
Aero/HS products
Net Sales:
Net sales			344.6	361.4
Automotive Extrusions
Net Sales:
Net sales			97.1	103.8
GE products
Net Sales:
Net sales			212.7	231.1
Other products
Net Sales:
Net sales			$ 23.7	$ 42.6
Fabricated Products
Net Sales:
Net sales	$ 334.9	$ 367.2
Fabricated Products | Aero/HS products
Net Sales:
Net sales	167.7	181.1
Fabricated Products | Automotive Extrusions
Net Sales:
Net sales	48.8	53.7
Fabricated Products | GE products
Net Sales:
Net sales	107.3	112.0
Fabricated Products | Other products
Net Sales:
Net sales	$ 11.1	$ 20.4