Discontinued Operations - Schedule of Loss from Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations, net of tax	$ (1.4)	$ (4.4)	$ (4.8)	$ (7.4)
Disposal Group, Held-for-sale, Not Discontinued Operations | Aluminum Products Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales	45.4	51.9	137.7	171.5
Cost of sales	41.6	52.8	129.6	165.5
Selling, general and administrative	4.9	3.3	12.5	10.6
Restructuring and other special charges	0.0	0.5	0.0	3.7
Operating loss	(1.1)	(4.7)	(4.4)	(8.3)
Interest expense	(1.1)	(0.6)	(2.6)	(2.0)
Loss from operation of discontinued operations	(2.2)	(5.3)	(7.0)	(10.3)
Income tax benefit	0.8	0.9	2.2	2.9
Loss from discontinued operations, net of tax	(1.4)	(4.4)	(4.8)	(7.4)
Interest expense allocated	$ 1.0	$ 0.5	$ 2.3	$ 1.7