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, 2022	Dec. 31, 2021	Dec. 31, 2020
Net sales:
Net sales	$ 3,427.9	$ 2,622.0	$ 1,172.7
Aero/HS products
Net sales:
Net sales	676.1	533.7	537.9
Packaging
Net sales:
Net sales	1,585.3	1,119.3
Automotive Extrusions
Net sales:
Net sales	254.8	225.0	161.4
GE products
Net sales:
Net sales	883.8	706.1	458.8
Other products
Net sales:
Net sales	27.9	37.9	14.6
Transferred at Point in Time
Net sales:
Net sales	2,782.9	2,067.9	690.9
Transferred over Time
Net sales:
Net sales	$ 645.0	$ 554.1	$ 481.8