Business, Product and Geographical Area Information - Net Sales by End Market Segment Applications (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Net sales:
Net sales	$ 807.6	$ 948.8
Aero/HS products
Net sales:
Net sales	214.0	176.6
Packaging
Net sales:
Net sales	354.2	448.0
Automotive Extrusions
Net sales:
Net sales	70.8	63.8
GE products
Net sales:
Net sales	162.1	251.2
Other products
Net sales:
Net sales	6.5	9.2
Transferred at Point in Time
Net sales:
Net sales	624.8	772.0
Transferred over Time
Net sales:
Net sales	$ 182.8	$ 176.8