Business, Product and Geographical Area Information - Net Sales by End Market Segment Applications (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net sales:
Net sales	$ 948.8	$ 324.0
Aero/HS products
Net sales:
Net sales	176.6	111.7
Packaging
Net sales:
Net sales	448.0
Automotive Extrusions
Net sales:
Net sales	63.8	57.6
GE products
Net sales:
Net sales	251.2	150.4
Other products
Net sales:
Net sales	9.2	4.3
Transferred at Point in Time
Net sales:
Net sales	772.0	200.2
Transferred over Time
Net sales:
Net sales	$ 176.8	$ 123.8