Business, Product and Geographical Area Information and Concentration of Risk - Net Sales by End Market Segment Applications (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net sales:
Net sales	$ 2,622.0	$ 1,172.7	$ 1,514.1
Aero/HS products
Net sales:
Net sales	533.7	537.9	803.2
Packaging
Net sales:
Net sales	1,119.3
Automotive Extrusions
Net sales:
Net sales	225.0	161.4	190.5
GE products
Net sales:
Net sales	706.1	458.8	480.1
Other products
Net sales:
Net sales	37.9	14.6	40.3
Transferred at Point in Time
Net sales:
Net sales	2,067.9	690.9	866.9
Transferred over Time
Net sales:
Net sales	$ 554.1	$ 481.8	$ 647.2